Three men, at least one of them carrying a.22 caliber pistol, were discovered on the second floor of Suitland High School yesterday afternoon by the school's principal, county officials reported.

According to John Aubuchon, spokesman for the Prince George's county schools, the men fled down a staircase and outside when Walter Battle, principal of the school on Silver Hill Road, approached them at 1:15 p.m. and asked them for a hall pass or identification cards.

As the group reached the bottom of the stairs, a pistol dropped from the pocket of one of the men, going off as it hit the ground, Aubuchon said. No one was injured by the shot.

The sound of the shot brought the school's vice principal and two teachers to the scene and they also began to chase the three men, who had fled toward Suitland Junior High School 200 yeards away.

When the three men left the school grounds the teachers gave up the chase and called the county police, Aubuchon said.

Sgt. Robert Law, public information spokesman for the county police, said that five policemen were sent to the school. The policemen combed the school grounds and, finding nothing, checked the surrounding streets, also without result.

Aubuchon said that even though the school security officer was not present at Suitland High School yesterday, "The principal is able to perform the same security function." The gun is being kept in a locked vault tonight, Aubuchon said. A school employe added that the weapon will be given to the school security guard tomorrow.