BARNI, Italy (AP) _ An Italian airliner carrying 37 people on a flight from Milan to West Germany slammed into the northern foothills of the Italian Alps during a heavy rainstorm Thursday night, authorities said.

There was no word on whether there were any survivors at the crash site on Mount Crezzo. One witness said he saw ''a ball of fire'' from where the plane apparently went down.

Driving rain, heavy fog and rough terrain hampered rescuers' efforts to reach the twin-engine turboprop plane, which crashed near Barni, a small town about 40 miles north of Milan.

Air traffic controllers lost contact with Flight 460 of the state-run Alitalia subsidiary ATI about 7:30 p.m. (2:30 p.m. EDT), 15 minutes after it had taken off from Milan's Linate Airport for Cologne, West Germany, said airline spokesman Roberto Panico.

Right before the plane vanished from the radar screens at 7:29 p.m., pilot Lamberto Laine radioed the control tower, ''We are in emergency,'' the news agency ANSA reported, adding that nothing else was heard from the plane.

Hundreds of rescuers poured into the area, marked by precipitous cliffs, crevices and thick woods, but officials said early Friday it was unlikely they would locate the plane before daylight.

News agencies and state-run RAI television quoted some officials as saying the plane apparently struck the 2,300-foot level of Mount Crezzo, near Lake Como. Local officials said the exact site had not been pinpointed.

''I heard a very loud noise, like a plane flying very low, and shortly thereafter a blast that shook the hotel,'' said Cinzia Barni, 25, daughter of the owner of the Italia Hotel. ''I ran outside and a boy told me that he had seen a flash of light on the mountain.''

At the Madonnina Refuge, an inn at about 3,280 feet elevation in the vicinity of Mount Crezzo, proprietor Franco Villa said he was eating dinner with his family when they heard a loud noise. Running to the window, they saw ''a ball of fire'' on the mountain, followed by the sound of an explosion, he said.

The plane was carrying 34 passengers and three crewmembers, Panico said. He said the plane, an ATR 42, was on a special flight carrying mostly employees of a German firm.

ANSA said five passengers were believed to be Italian, while the others were believed to be German. The three crewmembers were Italian, it added, and were identified as Laine; co-pilot Pierluigi Lampronti and flight attendant Carla Cornegliani. Panico said no passenger list was immediately available.

The crash site was a sparsely populated area between the southern two forks of poular Lake Como, about 16 miles from the Swiss border.

Spokesmen for the fire departments in the towns of Lecco and Como, both about 30 miles north of Milan, told The Associated Press that no dwellings appeared to have been hit in the crash.

They said rescue crews were combing the mountainous area by foot and four- wheel drive. Ambulances and helicopters were spotted on standby in fields in this town.

At the Cologne-Bonn airport, meanwhile, spokesman Hans Ley said relatives of the passengers had been informed of the crash, and that doctors and nurses had been called in to administer sedatives to stricken family-members.

Officials said it was the first major crash for Italian commercial aviation since July 1980, when an Italian DC-9 exploded mysteriously over the Mediterranean, killing 81 people.