Hundreds of corellas have been found dead in a suspected poisoning in the regional Victorian town of Horsham.

More than 50 birds were found dead near the Wimmera River on Tuesday last week, but the number has since risen to 300.

Horsham Rural City Council crews have been removing the bodies, both in the river and in the surrounding areas.

During the clean-up, crews found grain suspected to be poisonous.

Those grains have been vacuumed and covered up to prevent further harm to the local wildlife.

The Victorian conservation regulator is investigating the matter and has taken samples for testing to determine the cause of death.

Authorities are also awaiting test results to discover the type of poison used.

Corellas are protected under law and anyone illegally hunting, taking or destroying wildlife could face significant penalties, including imprisonment.

“It’s illegal and dangerous to poison wildlife, and we’re calling on the community to come forward with any information they might have that will help us to track down whoever is responsible,” conservation regulator chief Kate Gavens said.

The Victorian conservation regulator is urging anyone with information to come forward.

“The investigation of this incident is underway, and we need the community to call Crime Stoppers if they have CCTV footage or have seen anything suspicious, particularly along the Wimmera River at Horsham,” Gavens said.

Residents are urged not to touch or move dead or sick birds and, instead, take photos, record the location and report clusters of five or more to the Department of Energy, Environment and Climate Action.