Howard County police are investigating three Columbia robberies, including one of a cab-driver, that occurred late Thursday and early Friday.

Police said the robberies were not related.

About 10 p.m. Thursday, police said, a Columbia Cab driver was traveling in the 7200 block of Dockside Lane when he picked up a male passenger.

The passenger was joined by two others and then two more, police said. The robbers forced the driver onto the ground, stole his wallet, money and jacket, and fled, police said. The cabdriver was not injured.

Police are looking for five teen-agers, all under 5 feet 8 inches tall.

In a robbery about 20 minutes later, two men entered Video Systems in the 6000 block of Dobbin Road and told a clerk to open the safe, police said.

When the female clerk turned around, police said, one robber pointed a silver handgun at her.

The woman ran into a bathroom and locked the door, said police, who were not sure whether any money was taken.

About 4: 30 a.m. Friday, a man robbed the Mobil gas station in the 7200 block of Cradlerock Way, police said.

The man approached the clerk's window, displayed a handgun and demanded money, police said. The clerk handed over an undetermined amount of cash, and the robber fled.

Pub Date: 11/14/98