ALBANY, N.Y. (AP) _ Gov. Mario Cuomo's plane was forced to make an emergency landing at a small Pennsylvania airport after its occupants smelled smoke, and officials had no immediate explanation for the problem that led to the plane's third unscheduled landing in 1 1/2 years.

Federal Aviation Administration investigators arrived at the Williamsport airport today to look over the plane, which landed early Sunday after occupants reported smelling smoke, according to Thomas Hart, airport manager. New York state officials also planned to examine the plane, said Cuomo spokesman Terry Lynam.

It was not determined Sunday if there was a fire or just something overheating in the plane, said Gary Fryer, a spokesman for the governor. The plane was bring the governor home from a speaking engagement in New Orleans.

Cuomo and his aides smelled smoke at about 1:30 a.m., Fryer said. At the same time the two pilots started having trouble with the radio on the plane, which was flying through heavy rain and lightning, he said.

The pilots turned off all non-essential power, including the aircraft's interior lights, said Fryer.

Using flashlights to read their controls, the pilots landed at the Williamsport airport, which was closed. No one was injured, Fryer said.

The pilots were assisted in the landing by an unidentified pilot in another aircraft and by air traffic controllers in New York City, Boston and Altoona, Pa., said Fryer.

Because of the electrical problems, the aircraft's radios and navigational equipment were not working properly, said Fryer. So the unidentified pilot relayed information from air traffic controllers to the governor's pilots, he said. The helpful pilot also used his equipment to turn on the runway lights at the closed airport, he said.

Pilot Bud Hill told Fryer that the incident was ''potentially dangerous,'' but the governor's pilots maintained control of the plane.