A middle-aged man slipped a teller a note that said he had a gun and then made off with an undisclosed amount of cash from a Harvard Square bank Tuesday afternoon, police said.

Leona Davidson, at the Cambridge Savings Bank, 1375 Mass. Ave., told police that a man in his thirties walked into the bank at about 3:15 p.m. Tuesday and handed her a note that read, "I have a gun, give me 20's. 100's and 50's."

Bank officials yesterday confirmed that the branch had been robbed, but would not disclose how much money the bandit took.

"We can't really make a comment except that yes, there was a robbery. "Peter A. Rattigan, the assistant treasurer of the branch across the street from Harvard Yard, said yesterday.

Lt. Timothy J. Toomey of the Cambridge Police said yesterday that detectives are pursuing leads and have a suspect in the case.

Toomey added that Cambridge Police are cooperating with the Federal Bureau of Investigation.

The teller described the suspect as a white male in his thirties, five feet, nine inches tall, medium weight, with brown hair and brown eyes.

Other incidents reported to Cambridge and Harvard University Police during the period from March 9 to 15 include.

Fire, Vandals Hit Science Center: Authorities are investigating a fire that broke out early Monday morning at the Science Center loading dock.

The blaze, which Fire Department officials labelled suspicious started in a stack of computer printout paper inside the building near the loading platform at about 2:30 a.m., police said.

Ronald R. Vanelli, the director of the Science Center, said yesterday that the fire, which firefighters said set off the sprinkler system, did not cause any damage.

Cambridge firefighters extinguished the fire in a matter minutes, Lt. Michael R. Travers of the Cambridge Fire Department, said yesterday.

Travers said the cause of the blaze is still under investigation.

Police reported they were called to the Science Center a few moments before that fire is believed to have started on a report of vandalism. Police reported that someone had tried to tear down on of the basement mens' room stall doors.

Computer Stolen: A desktop computer valued at $6.000 was reported stolen last weekend from the Office of Financial Systems (OFS) at Holyoke Center, police said.