Leading Senior Constable Nathan Cashion, of the Portland police, said the accident happened on a bush track in a remote area of the forest about 12.30pm.

With no mobile phone reception where the accident happened, one of the injured riders was able to ride back to another area where he was able to call for help, Leading Senior Constable Cashion said.

“He’s done a huge effort to get to where there’s reception,” he said.

With the riders located in two different locations, a request was made for the air ambulance to help locate the pair, Leading Senior Constable Cashion said.

He said police were still investigating just how the accident happened.

Ambulance Victoria spokesman John Mullens said one of the riders, a man aged in his 20s, was taken to Warrnambool Base Hospital in a stable condition with shoulder injuries.

The other rider, another man also in his 20s, suffered serious abdominal and pelvis injuries and would be flown to a Melbourne hospital, he said.

Both riders were believed to have been from the Warrnambool area.

Police have urged riders to be aware this summer of fenced-off areas in parks and forests.

“They need to be aware that some areas are out of bounds,” Leading Senior Constable Cashion said.