Two of the most seriously hurt passengers of a Red Arrow bus that rolled north of Edmonton Friday remain in hospital, say RCMP.

Both are in stable condition, says Sgt. Jennifer Jackson.

Thirty-one people were taken to hospital in Edmonton when the bus travelling from Fort McMurray flipped over on Highway 28 near near Redwater, about 65 kilometres northeast of Edmonton.

Most had just minor cuts and bruises, but three passengers were critically injured in the crash.

The crash is still under investigation, but conditions on the road were dry and the weather was sunny when the bus flipped on the two-lane highway.

RCMP have ruled out drugs or alcohol as factors in the accident.

Jackson said the investigation will take time because of the large number of people to interview.