Melbourne Cup-winning trainer Darren Weir is one of two men being questioned by police over allegations of corruption and the use of electric-shock devices on racehorses.

Three men were arrested on Wednesday during raids of properties – including stables – at Ballarat and Warrnambool, found four taser-like devices, known as “jiggers” in the racing industry.

One of the trio – a 26-year-old – was released pending further investigation, Victoria Police Assistant Commissioner Neil Paterson said, adding that the complex investigation stretched back to August last year and involved allegations of corruption in sport.

“I have heard that there may be footage in the public arena … of jiggers being used,” Mr Paterson said, appealing for people with information to come forward.

Weir, 48, and a 38-year-old Yangery man remain in custody.

Mr Paterson said an unregistered firearm and three jiggers were seized from one property during the raids, and a fourth device and suspected quantity of cocaine at a second.

Racing Victoria boss Giles Thompson refused to identify the parties involved, other than to confirm each is a licensed participant in the state's racing industry.

“Racing Victoria's primary objective is to protect the integrity of the sport … and ensure a level playing field for all,” he said.

Racing Victoria alerted Victoria Police after launching investigations into parties last year.

Weir is Australia's most prolific and successful trainer and trained the 2015 Melbourne Cup winner Prince of Penzance.

Victorian Racing Minister Martin Pakula said the investigation showed authorities were enforcing rules “without fear or favour”.

“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 in a statement.

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