BYRON, N.Y. (AP)  -- A fire in a small apartment complex in rural upstate New York early Monday killed a mother, her teenage son, and two daughters recently returned from college for the summer break.

The bodies were recovered during an hours-long search in the smoking rubble of the four-unit, two-story building in farm country 25 miles west of Rochester.

Neighbors said the boy was a 17-year-old junior at Byron-Bergen High School and the daughters attended colleges in New York City and Binghamton and returned home just last week. Their identities will likely be withheld until Tuesday when autopsies are completed, the Genesee County sheriff's office said.

The cause of the blaze wasn't immediately known.

Firefighters were called to the cluster of duplex apartments at around 4:30 a.m. Monday and took about two hours to bring the fire under control, said Byron Fire Chief John Durand said. The blaze spread quickly to the adjoining apartments and at least 10 neighbors escaped before fire crews even arrived, Durand said.

``It had a big head start on us,'' Durand said. ``The flames were coming out the lower windows, both front and rear about 7 or 8 feet and in the air about 15 to 20 feet.''

The fire apparently originated in the apartment where the family lived, and ``it's either got to be electrical or a furnace or hot water heater or something on that order,'' Durand said.

The 1970s-era building sits next to a two-lane road across from a plowed field that stretches for a half-mile to a rows of trees on the horizon. Smoke detectors in the complex were tested about two months ago and worked ``but I didn't hear them when I got here,'' Durand said.

The bodies of the mother and one of her daughters were found quickly, one on each floor, but the other victims were not recovered until Monday afternoon on the ground floor. The fire collapsed the first-floor ceiling and the entire building was heavily damaged.