Authorities arrested a Gaithersburg man last night who investigators believe robbed at least 11 banks in the Washington and Baltimore suburbs over the past month, passing notes to tellers and implying that he had a weapon.

Plainclothes detectives from Montgomery and Prince George's counties located Christopher M. Cline at a Prince George's County hotel about 6 p.m. and took him into custody without incident, police said.

Cline, 28, who is suspected of robbing banks in Montgomery, Prince George's, Howard and Baltimore counties, had been sought by investigators from those counties, the U.S. Marshals Service, the FBI and a regional fugitive task force, said Lt. Eric Burnett, a Montgomery County police spokesman. He has been charged in warrants in at least two robberies.

Investigators linked the cases through witnesses' description of the man and the way in which the banks were robbed, authorities said. Burnett said police obtained an arrest warrant last weekend after connecting Cline's name with the face that had been photographed by bank security cameras.

Police provided few details last night of what had led detectives to the hotel, which they would not identify.

"It was just good police work. The old kind of police work," Burnett said.

Cline is believed to be responsible for at least three Montgomery County bank robberies, at the Sandy Spring Bank at 13300 New Hampshire Ave. in Colesville on Nov. 8, the SunTrust Bank at 12500 Prosperity Dr. in White Oak on Nov. 12 and the Chevy Chase Bank at 14949 Shady Grove Rd. in Rockville on Nov. 13, police said. He also is believed to have tried unsuccessfully Nov. 12 to rob the Chevy Chase Bank at 11261 New Hampshire Ave. in White Oak, police said.

Suzanne Cline, his stepmother, said last night that Christopher did "one thing wrong" as a teenager and "got caught up in the system. When Chris was young he was a beautiful child. We don't know why Chris did this."

In Prince George's, police say Cline is a suspect in the Nov. 10 robbery of a SunTrust Bank at 2520 University Blvd. in Adelphi and the holdup Tuesday of a Sandy Spring bank in Laurel. In Howard County, Cline is believed to have robbed the Citizens National Bank in Elkridge on Oct. 25 and a SunTrust Bank in Columbia on Nov. 3, police say.

Authorities would not say how much money was stolen from the banks.

Investigators from Montgomery County and the FBI interrogated Cline at police headquarters in Rockville last night, and he was to go before a magistrate for a bond hearing. It was unclear when officers from other jurisdictions would begin to interview Cline, Burnett said.