MOSCOW (AP) — A Russian aviation agency has ordered the operator of a plane that crashed near Moscow last month to ground four other such aircraft in its fleet.

The agency, Rosaviatsiya, said Tuesday it told Saratov Airlines to ground its An-148 planes, one of which crashed Feb. 11 and killed 71 people. The twin-engine plane crashed minutes after taking off from a Moscow airport.

Rosaviatsiya also said its check of the airline has found unspecified violations.

After studying the An-148's flight data recorder, the Interstate Aviation Committee said last month the crash occurred after the pilots saw conflicting data on the plane's two air speed indicators. The committee said that flawed readings came because the pilots failed to turn on the heating unit for the plane's pressure measurement equipment prior to takeoff.