A Novato man was in critical condition Tuesday following a Highway 101 crash Monday night.

CHP officers Tuesday were attempting to learn what caused driver Thomas Umphreys, 48, to lose control of his sedan as he headed south on Highway 101 near Cotati.

Umphreys suffered life-threatening injuries and was being treated at Santa Rosa Memorial Hospital.

He'd been driving in a Toyota Corolla at about 65 mph when he crashed about 8:10 p.m., CHP Officer Jon Sloat said.

At the top of the Cotati Grade, south of Railroad Avenue, the car veered to the right, ran up an embankment and flipped over, Sloat said. It stopped on its roof, trapping Umphreys, who was freed by Rancho Adobe firefighters.

Passengers Angeliki Vartholomeos, 33, of Mill Valley and daughter Francis Daverm, 3, got out of the wreckage with minor injuries. They were taken to Petaluma Valley Hospital.

CHP investigators were looking into whether drugs or alcohol were a factor, said Sloat.