Victoria Police says it has seized a number of illegal items, including cocaine, an unregistered firearm and the jiggers as part of the early morning raid.

In a press conference in Melbourne, Assistant Commissioner Neil Paterson outlined the extent of the investigation.

Assistant Commissioner Paterson said there was also evidence to suggest a video existed of jiggers being used, which was central to the investigation.

Weir has since been released from the Ballarat West Police Station without charge, where he gave the thumbs up the media.

The other two men have also been released.

Four Warrnambool properties and two Ballarat properties were raided.

Among other charges, police are also investigating possible animal cruelty breaches.

Police say the investigation has been under way “in ernest” since at least August, 2018.

“I have heard there may be footage in the public arena of jiggers being used,” Assistant Commissioner Paterson said.

“The allegation is they may be used against a horse with the aim of improving the performance of a horse on a particular raceday.”

No charges have yet been laid against Weir or the other man arrested.

Police said they were still investigating a number of matters including:

Weir has not yet been banned from competing, although Racing Victoria CEO Giles Thompson said racing stewards would determine if Weir would be stood down in the future.

He is due to have five runners in Mornington today.

​Watch the full press conference here.

UPDATE, 12.54PM: Police say they will hold an official press conference at 1.30pm in Melbourne.

Victoria Police Assistant Commissioner Neil Paterson and Racing Victoria CEO Giles Thompson are expected to speak.

UPDATE, 12.15PM: Despite being arrested this morning following raids on his Ballarat stables, Darren Weir will still have a handful of runners go around at today's twilight meeting at Mornington.

Racing Victoria has not charged the 48-year-old trainer with a breach of the Rules of Racing, although he is being investigated by Victoria Police.

RELATED: From zero to hero; how Darren Weir rose to the top

He has five runners listed to race today, nine at Moonee Valley tomorrow night and 11 at Caulfield on Saturday.

Victorian racing minister Martin Pakula has released the following statement.

“I’m aware of an investigation into the activities of licensed persons in the Warrnambool and Ballarat area by Racing Victoria’s Integrity Services and Victoria Police’s Sporting Integrity Intelligence Unit,” he said.

“As Minister for Racing and a racing lover, I’m committed to maintaining the integrity of our sport and any allegations of breaches are extremely disappointing.

“This investigation demonstrates that integrity officials of Racing Victoria will enforce the rules of racing without fear or favour.

“As the matter is subject to an on-going investigation by Victoria Police and Racing Victoria, it would be inappropriate to comment further.”

UPDATE, 11.50AM: A Ballarat racehorse owner who has had horses with Darren Weir for more than 10 years said today’s raids were something he never wanted to see.

“You hope something never happens, but there’s always the fear that it might,” said the owner, who did not wish to be named.

“There’s a lot of talk around, we’re not sure what’s happening at the moment.”

The Courier spoke to numerous businesses throughout the township this morning, who did not wish to comment on the specifics.

One businesses owner, who also did not wish to be named, said racing played an important part in the town and had become the main industry in Miners Rest, which was helping the township and the entire Ballarat region grow.

Another business said they had heard “something was happening” up at the stables, but did not know any details.

Another said the first they knew about something going on was when they heard the news first thing in the morning.

UPDATE, 11.24AM: Ballarat Turf Club chief executive Lachlan McKenzie said he was shocked and surprised by the developments at Darren Weir’s stables this morning.

McKenzie told The Courier that he didn’t have any involvement or knowledge of the police raids other than what had been relayed by the media.

He said that it was too early to comment any further on the matter.

Weir has been integral in building the stature of the club’s training base and regularly praises its facilities, including the high profile uphill galloping track.

Many other trainers have since joined the Miners Rest precinct on the back of his overwhelming success.

EARLIER: Melbourne Cup-winning horse trainer Darren Weir and two other men have been arrested after twin raids of stables in Ballarat and Warrnambool.

A number of items, including a gun and what is thought to be a Taser, have also been seized.

Uniformed and plain-clothed officers swooped on stables owned by Weir at Miners Rest and in Warrnambool early on Wednesday morning.

Weir, 48, from Miners Rest, a 38-year-old Yangery man and a 26-year-old Warrnambool man were arrested, and a number of items - including a firearm and a conducted energy device - were seized.

Detectives from Victoria Police's Sporting Integrity Intelligence Unit will now interview the three men.

Racing Victoria's executive general manager of the integrity unit, Jamie Stier, confirmed three people had been arrested as they investigated potential offences against the rules of racing.

“Racing Victoria’s Integrity Services team has been conducting an investigation into the activities of licensed persons in the Warrnambool and Ballarat areas," he said.

"During the course of our investigation we sought the support of Victoria Police’s Sporting Integrity Intelligence Unit on the matter, instigating their investigation.

“The Sporting Integrity Intelligence Unit this morning executed warrants at properties in Warrnambool and Ballarat where they arrested three licensed persons for questioning."

Police have also been investigating the house on the property.

A Victoria Police spokeswoman said the trio would be interviewed in relation to sporting integrity matters, including:

The raids are part of a continuing investigation. No charges have been laid. There is no suggestion the allegations are true, only that they are being investigated.

Due to the ongoing investigation, he would not comment on the identities of those arrested or the details of the investigation.

At about 6am, Racing Victoria compliance team officials and Victoria Police sports integrity unit officers took part in the searches.

It is understood some vehicles and cars were also examined at Warrnambool and Ballarat.

There have been persistent rumours during the past two months of a significant investigation.

The RSPCA said it was unaware of any investigation when contacted by The Warrnambool Standard in the past two weeks.

RSN Racing & Sport radio reports federal police visited Weir’s Ballarat stables some weeks ago where they may have seized an item central to an on-going inquiry.

Weir has five runners due to race at Mornington on Wednesday.

He was in New Zealand at the Karaka Sales on Sunday.

Weir, 48, has been training horses since 1995, recently taking out the Melbourne Cup with Prince of Penzance in 2015.

He is currently the most successful trainer in the national trainer's premiership, and counts hundreds of horses as part of his stable.

Born in Berriwillock, a small Mallee District town in Victoria, Mr Weir left school at age 15 to work under experienced trainers.

He moved to Ballarat in 2001 and later acquired stables at Warrnambool to compliment his Ballarat base.

Weir holds the Commonwealth training record for most number of wins in a season, first breaking it in season 2015/16 with 348 wins, and eclipsing it again each year since.