An escape attempt by nine inmates of the Prince George's County jail who used hacksaw blades to cut through steel bars was thwarted last night by officials acting on a tip. Five of the nine inmates had been returned to the jail after a successful escape last month, authorities said.

The nine were seized about 9:30 last night as they were preparing to saw through the bars on a first-floor corridor window of the maximum security section of the jail in Upper Marlboro, according to authorities.

Before being caught, the nine had cut through three steel bars separating a dayroom area and the corridor, and had removed an air conditioner from the window, which was barred on the outside, authorities said.

The attempt was foiled through "information developed mutually by the Department of Corrections and the Prince George's County sheriff's department," said Jim O'Neill, a spokesman for the Corrections Department.

He said that authorities are investigating how the inmates obtained the hacksaw blades used in the attempt.

In the escape last month, nine prisoners escaped from the jail after cutting through a third-floor window with a hacksaw. The nine apparently jumped to the ground or lowered themselves with ropes. Six of the nine who took part in the escape have since been recaptured.

The five involved in last night's attempt were identified by O'Neill as Andre Phillips, Harold Roberts, Robert Rogers, Labron Rudisill and Frank Washington.

After being recaptured following the July escape, the five were placed in the jail's maximum security area. They and the other four inmates involved in last night's attempt had been held in five separate cells in that area, in the older portion of the jail, the corrections spokesman said.

It was not immediately clear whether they had been in the cells immediately before the attempt began.