The paramedics' ambulance left the road in a narrow and twisting section of Highway 4 on Vancouver Island. (CBC)

Two paramedics have died after their ambulance crashed into a lake near Tofino on Vancouver Island, officials say.

The ambulance went off Highway 4 and plunged into Kennedy Lake early Tuesday while heading back to Tofino after transferring a patient to Port Alberni.

The vehicle is believed to have left the road sometime after 4 a.m. PT, police said.

No patient was aboard the ambulance at the time.

A dive team later recovered the bodies, said paramedics union spokesman William Chut.

No names have been released.

It's not known what caused the accident, which happened on a narrow, twisting stretch of the highway.

Ucluelet Mayor Eric Russcher said he's complained several times about the road because it can be dangerous.