Several bones discovered on a popular holiday island are human, police have confirmed.

The remains were found Wednesday on Rottnest Island, off the coast of Perth, during construction work at the grounds of the Holy Trinity Church.

The work was being carried out as part of a bus stop project.

Pictures from 7NEWS showed the scene had been cordoned off while officers investigated.

A forensic pathologist determined the bones recovered are human, WA Police said on Thursday.

The remains were taken to Perth with further forensic assessment to reveal how old the bones are.

Inquiries are continuing.

Police have confirmed bones found on Rottnest Island are human.Police have confirmed bones found on Rottnest Island are human. Credit: 7NEWS The bonest were found during construction work.The bonest were found during construction work. Credit: 7NEWS

It comes as police investigate a serious bicycle crash on the island that left an international tourist fighting for life.

The 38-year-old woman fell from her bike on Digby Dr in the Thompson Bay area about 5pm on Tuesday.

She suffered serious, life-threatening head injuries and was flown from the island to Royal Perth Hospital in a critical condition.

“The circumstances surrounding the crash remain under investigation,” WA Police said.

Rottnest, also known as Wadjemup, is a car-free island located 20km off the coast from Fremantle.

It is home to the quokka and is famous for its picturesque beaches, shipwrecks and secluded bays.