BELMONT, Mass. (AP) — Authorities say one person has died in an early morning house fire in Belmont.

Chief David Frizzell says residents of the first- and second-floor apartment escaped safely from the three-alarm blaze reported at about 4 a.m. Monday but a man was found dead in the third-floor unit.

The victim's name was not immediately released.

Frizzell says the fire was well advanced by the time firefighters arrived.

The fire on Trapelo Road, a main artery through the town, is expected to cause rush hour headaches for commuters as the road remains closed during the investigation.

Waltham and Cambridge firefighters assisted at the scene.