Police have charged Melbourne Cup-winning horse trainer Darren Weir and two other men with animal cruelty offences following raids on Weir's stables near Ballarat and Warrnambool in January this year.

Key points: Police said four men were charged as part of an investigation into alleged illegal activity in the racing industry

Police said four men were charged as part of an investigation into alleged illegal activity in the racing industry Weir and two of the men were charged with six counts of animal cruelty offences each

Weir and two of the men were charged with six counts of animal cruelty offences each The fourth man was charged with a betting-related offence

In a statement, Victoria Police said detectives from its Sporting Integrity Intelligence Unit had charged four men on summons as part of an investigation into alleged illegal activity within the racing industry.

The fourth man was charged with one count of "use of corrupt conduct information", a betting-related charge.

Weir, 49, was charged with a total of nine offences including three counts of "engaging in the torturing, abusing, overworking and terrifying" of a thoroughbred racehorse and three counts of "causing unreasonable pain or suffering" to a racehorse.

Police laid the charges more than eight months after Weir's properties were raided. ( ABC News: Daniel Miles, file photo )

Other charges included possession of an unregistered firearm and conspiracy to defraud Racing Victoria stewards.

Who is Darren Weir? Born in the town of Berriwillock in Victoria's north-west

Born in the town of Berriwillock in Victoria's north-west Left school at 15 and began work in the horseracing industry

Left school at 15 and began work in the horseracing industry Took out his own trainer's licence aged 25, when based at Stawell

Took out his own trainer's licence aged 25, when based at Stawell Expanded operations to Ballarat and Warrnambool as his success grew

Expanded operations to Ballarat and Warrnambool as his success grew Won 348 races in the 2015-16 season, setting a new Commonwealth training record

Won 348 races in the 2015-16 season, setting a new Commonwealth training record Trained the 2015 Melbourne Cup winner Prince of Penzance

A 38-year-old Yangery man was charged with 16 offences including the same number of animal cruelty charges as Weir, engaging in conduct that would corrupt betting outcomes and possessing cocaine.

A 27-year-old Warrnambool man was charged with the same six counts of animal cruelty offences as well as conspiracy to defraud stewards.

The charges come after police raided Weir's properties at Miners Rest, near Ballarat, and Warrnambool on January 30.

Racing Victoria has ordered licensed trainer Jarrod McLean and two registered stable employees, Tyson Kermond and William Heman, to attend hearings in Melbourne on Tuesday.

"Upon the issuing of the charges today our [Racing Victoria] stewards have immediately opened inquiries and ordered three persons to attend … to answer questions in relation to the charges," Racing Victoria said in a statement.

"These are serious charges and the nature of the alleged conduct described … is distressing to all."

In February, Racing Victoria suspended Weir for four years after police allegedly found electrical devices used to shock horses, known as "jiggers", in the raids.

Weir, who trained the 2015 Melbourne Cup winner Prince of Penzance, was widely regarded as Australia's leading horse trainer before the raids on his properties.

All four men are due to appear at the Melbourne Magistrates' Court on October 23.