Three Montgomery County men were injured, two of them critically, when the single-engine private plane in which they were flying struck electric lines and crashed last night in Frederick County, the county sheriff's department reported.

Those injured in the 9:30 p.m. crash, which occurred near Frederick, were identified as Douglas Powell, 30, and Ronald Smith, 43, both of Rockville, and James Garner of Gaithersburg.

They had taken off from Seven Springs, Pa., and were headed for the Montgomery County Airpark, according to the sheriff's department.

Authorities said the plane had been losing altitude and that it struck power lines near a housing complex, and then came to rest upside down in an open field near I-270.

Garner and Smith were taken to the shock trauma unit at the University of Maryland hospital in Baltimore, authorities said.

The sheriff's department said both were reported in critical condition.

Powell was listed in good condition at Frederick Memorial Hospital.

The cause of the crash was not immediately known. However, a spokesman for the sheriff's department said the plane may have experienced a fuel problem.

He said the Federal Aviation Administration was expected to investigate.

It was not immediately known which of the three men was the pilot.