Leading rider David Pires suffered a fractured hip and could be sidelined for several months while fellow jockey Shuji Amano sustained a broken collarbone.

Jason Maskiell, Bulent Muhcu and Georgie Catania were all treated in hospital and released.

The fall happened near the 600m in the opening race.

Pinkeyes Pride (Amano) was at the head of the field, inside another runner, when it stumbled badly and dislodged its rider.

In a chain reaction, Grave Digger (Pires) fell and Zipponet (Maskiell), Jewels (Muhcu) and Miss Buzz (Catania) all lost their riders.

Grave Digger had to be put down due to its injuries but the other horses appeared unhurt and galloped riderless down the home straight.

Tasmanian Jockeys’ Association general manager Kevin Ring reported that Pires would need surgery to repair damage to a hip joint.

The injury couldn’t have come at a worse time for the dual Hobart Cup winner, with the Launceston Cup carnival starting on Sunday.

Pires is the stable rider for leading trainer Scott Brunton and would have been guaranteed rides in most of the major races.