They also said they were investigating the use of electronic shock devices known as "jiggers”. 

Assistant Commissioner Neil Paterson said stables on McGregors Road, at the city’s racecourse and a Belmore Road property in Warrnambool and two properties at Yangery - Conns Lane and Caramut Road - were searched.

He confirmed a 26-year-old Warrnambool man, who had been arrested this morning and questioned, had been released pending further inquiries.

Extensive searches were conducted at properties in the south-west and at Miners Rest, near Ballarat, with some still ongoing.

An unregistered firearm, four jiggers and a small quantity of cocaine were found, Assistant Commissioner Paterson said. 

He said police were investigating allegations of animal cruelty, relating to the use of the jiggers, as well as allegations of corruption in racing.

“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.”

He said police became involved in the investigation in August at Racing Victoria’s request.

Police declined to name the three men who had been arrested and questioned. 

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.

UPDATE 12.15pm: State Government Racing Minister Martin Pakula has released a statement saying he is aware of the “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”.

“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,” he said.

“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 NOON: Warrnambool Racing Club chief executive officer Peter Downs has declined to elaborate on this morning’s police raids and arrests, saying it was an ongoing police investigation. 

"Integrity is the most important thing in this matter," he said.

"It's a matter for the stewards and police."​

UPDATE 11.15am: 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 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.

UPDATE 8.48am: Victoria police have confirmed three people have been arrested including a 48-year-old Miners Rest man, a 38-year-old Yangery man and a 26-year-old Warrnambool man.

They will now be interviewed in relation to sporting integrity matters including obtain financial advantage by deception, engaging in conduct that corrupts or would corrupt a betting outcome of event or event contingency, use of corrupt conduct information for betting purposes, and attempt to commit indictable offence namely obtain financial advantage by deception.

A number of items including a firearm and what is believed to be a conducted energy device were also seized from the properties.

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.

UPDATE 8.45am: Three people have been arrested following the raids, Racing Victoria said.

In a statement, Racing Victoria said its integrity services team had conducted raids.

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

“The Sporting Integrity Intelligence Unit this morning executed warrants at properties in Warrnambool and Ballarat where they arrested three licensed persons for questioning. Members of the Racing Victoria Integrity Services team attended licensed stables to assist Victoria Police and to investigate potential offences against the Rules of Racing.

“As the matters are the subject of on-going investigations by Victoria Police and Racing Victoria we are not at liberty at this time to disclose the identities of the persons arrested nor the details of the investigations.

“Racing Victoria is committed to maintaining the highest integrity standards in our sport and, where appropriate, we will continue to work with Victoria Police on those investigations.”

Earlier: Leading Australian racing trainer Darren Weir had stables at Warrnambool and Ballarat simultaneous raided pre-dawn this morning.

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

Sources have told The Standard that up to 20-armed officers corralled the stable’s staff at Warrnambool.

It's 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 Standard in the past two weeks.

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.

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