MELBOURNE (Reuters) - Australian police raided the stables of Melbourne Cup-winning trainer Darren Weir on Wednesday as part of an ongoing investigation into corruption and the possible use of electric-shock devices on horses.

Three men, aged 48, 38 and 26 were all arrested on warrants in relation to sporting integrity matters, Victoria Police said in a statement.

The trio were later released pending further investigation, Victoria Police Assistant Commissioner Neil Paterson said, adding the investigation stretched back to last August and involved allegations of corruption in sport.

“This is a complex investigation making an assessment of many aspects of evidence and I anticipate that assessment will take some time before we can make decisions in context of charges,” Paterson said.

Neither Victoria Police, nor Racing Victoria, would confirm whether Weir, who trained Prince of Penzance to Melbourne Cup victory in 2015, was among the three men arrested in the raids at properties in Ballarat and Warrnambool in rural Victoria.

Paterson had earlier said that four electric-shock devices, known within the industry as ‘jiggers’ and which are outlawed, had been discovered at the properties.

“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.

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

Local media, however, reported that Weir, 48, was one of the people arrested.

Racing Victoria alerted Victoria Police after launching investigations last year, Thompson added.

Weir made history in 2015 when Prince of Penzance held off Max Dynamite to win the Melbourne Cup, with Michelle Payne becoming the first female jockey to win the richest and most celebrated horse race in Australasia.