ROME (AP) _ The altimeter of a Marine jet that severed a ski gondola cable in the Alps last month appeared to be functioning properly, according to tests Tuesday, the ANSA news agency reported.

An altimeter measures altitude, in this case how high the plane was off the ground. The tests are part of an investigation to uncover whether pilot error, equipment failure or a combination of factors was to blame for sending 20 people in the cable car plummeting to their deaths.

The tests were requested by a lawyer for the four-man crew of the EA-6B Prowler who said the altimeter may not have been working when the jet severed the cable Feb.3.

The ANSA report cited a source who participated in the tests on the altimeter, but did not identify that person. Additional tests would be carried out Wednesday, according to ANSA.

The tests were carried out at Aviano, the U.S. air base in northern Italy, where the crew is on temporary duty. It was part of the Italian civil investigation into the tragedy.

A U.S. military panel also is investigating. The Italian air force has blamed pilot error, saying the jet was too low and off course.

The jet was on a training run when it sliced the cable with its right wing. Capt. Richard Ashby and his three-man crew were flying below the cable's highest point of 400 feet when the plane hit it.

Italy does not allow aircraft on training flights to dip below 2,000 feet, although American regulations permit pilots to fly as low as 1,000 feet.