While workers were installing bulletproof glass last weekend in the tellers' windows in the aftermath of two robberies at the United Bank and Trust Co. of Maryland in Camp Springs, robbers struck again, this time three miles away at the bank's Clinton branch.

"Our people are very concerned with this," said James M. Lyon, manager of the Camp Springs branch, which was robbed twice in January. "It's scary because you don't know what they [robbers] are going to do. They are in control because they have a weapon and everyone's life is at stake."

The FBI believes that the two men who robbed Lyon's bank have committed a total of eight bank robberies in Prince George's County and Northwest Washington since December and may be tied to four additional robberies in the District this year.

"It appears as though it could be the same individuals" in all 12 robberies, said Victor R. O'Korn, special agent in the FBI's Washington field office. However, he said, "Right now the MOs [modus operandi] are different," leading investigators to believe that eight banks have been robbed by the same two men, while a third man has robbed four others.

The robberies usually occur during the afternoon hours, O'Korn said, and one person acts as a lookout in the lobby while the other enters the bank on a "business pretext," such as asking for a roll of quarters. He then announces the robbery and usually puts the money into a white plastic bag with red lettering before fleeing on foot, he said.

In all of the holdups except two, he said, the men have indicated that they were armed. During a robbery Feb. 13 at the Columbia First Federal Savings and Loan, 1800 M St. NW, one of the men displayed a handgun, he said, and during another a man presented the teller with a "demand note."

In addition to the Camp Springs branch of the United Bank and Trust Co., the men are suspected of twice robbing the Columbia First Federal Savings and Loan branch at 5301 Wisconsin Ave. NW.

Surveillance photographs show that in at least three instances, the men were in the bank at the same time, O'Korn said. During the other robberies, he said, "We have reason to believe that the other guy is outside in a getaway vehicle.

"One of the guys appears to know what he is doing," and after feeling for an explosive red dye pack planted with the loot, he has left the dye pack in the bank. However, during two recent robberies in Maryland, the other man has had a dye pack explode but has managed to escape despite being splattered with the dye.

Between the Dec. 28 robbery at the Equitable Federal Savings and Loan, 4505 Wisconsin Ave. NW, and the most recent one last Saturday at the United Bank & Trust Co., 9131 Piscataway Rd. in Clinton, the robbers have frequently changed their appearances, most often by adding a mustache or beard, O'Korn said.

However, based on "excellent" surveillance photographs taken during six of the holdups, witnesses' accounts and the similarity of methods used in the robberies, the FBI has concluded that the same men have robbed eight banks, netting them a total of $15,000 to $20,000, he said.

D.C. police are also investigating four bank robberies that are believed to have been committed by one man, who enters the bank, gives a teller a note demanding money and places the money in a newspaper or envelope, according to Capt. John W. Taylor of the D.C. police robbery squad.

Taylor said the man is suspected in five robberies, all in the 4000 and 5000 blocks of Connecticut and Wisconsin avenues NW, that occurred in the morning hours.