Investigators issued a sketch yesterday of one of the men suspected in a recent string of armed bank robberies in the District and Maryland.

Release of the sketch suggests that at least one witness to the most recent holdup saw a robber without his mask, or that police have had another break in the case. But in a briefing late yesterday afternoon, D.C. police would say only that "information" had yielded the sketch.

Investigators hope the sketch will help them identify the people responsible for the robberies before they strike again.

The robbers have hit six banks -- four in the District and two in Prince George's County -- and escaped with about $370,000. Each time, they have been armed with high-powered rifles and outfitted in masks and bulky clothing that may cover body armor. They act with military-style precision in teams of three or more.

But until the most recent holdup Tuesday at a SunTrust Bank branch on Connecticut Avenue NW, investigators apparently had little idea what any of the robbers looked like. Surveillance photographs taken in the robberies showed the men in action, but their faces were covered.

A number of people, including a television cameraman, were on the streets around the SunTrust Bank when the robbery began late Tuesday morning, and the escape was captured by a photographer from WTTG-TV (Channel 5) in chilling footage.

Nowhere in the footage that was broadcast do the faces of the robbers appear to be visible, but what witnesses on Connecticut Avenue saw in the moments before the camera began rolling is unclear.

After screeching away from the bank in a stolen minivan, the robbers ditched the vehicle a couple of miles away in a quiet residential neighborhood. As they have done in all but one of their earlier robberies, they set the minivan on fire, in an apparent attempt to destroy evidence, such as sweat deposits.

D.C. Police Capt. Michael Reese said the person depicted in the sketch is a light-skinned black man in his mid-twenties to early thirties. Reese said the man is between 6 feet and 6-3 and has a slim to medium build.

Police and the FBI consider the robbers to be extremely dangerous and urge anyone who has information about them to call police at 202-727-9099 or the FBI at 202-278-2000. The FBI is offering a $50,000 reward for information leading to arrests.

The amount taken in the robberies has ranged from about $140,000 Jan. 22 at a Bank of America branch on Blair Road NW to about $8,000 June 12 at an Industrial Bank branch on Rhode Island Avenue NE.

Reese said capturing the men is an urgent priority for authorities in the region.

"It's important to the city of Washington and also to the whole metropolitan area," he said. "These suspects have shown more than a slight propensity for violence."

Sketch shows one of the suspects.