City police are investigating another bank robbery after a masked man walked into a BB and T at 300 S. Washington St. on Saturday and demanded money.

The suspect, described as a 6-foot black man weighing about 170 pounds, entered the bank about 10:50 a.m. He implied possession of a weapon and asked for cash, police said.

After a teller turned over an undisclosed amount of money, the suspect, donning a mask and wearing a dark shirt and pants, fled the scene on foot. He remains at large, police say.

The heist marks the city’s fourth bank robbery of 2011 and the 16th since January 2009.

Authorities urge anyone with information about the heist to contact Detective Thomas Buckley at 703-746-6837 or the police department’s criminal investigations section at 703-746-6711.