The San Francisco Police Department sent extra officers into a Visitacion Valley housing project today following the shooting death of a 16-year-old boy late Monday.

Mark Crawford of San Francisco was shot about 10:15 p.m. in the Sunnydale public housing development, on Blythedale Avenue two blocks north of Geneva Avenue. He was pronounced dead at the scene.

Police spokesman Sgt. Wilfred Williams said Crawford was from the area but had recently moved away. He had come back for a visit when he was slain, Williams said.

No arrests have been reported in the slaying. Williams said it was unclear whether Crawford had any gang affiliations, or if there was another motive for the shooting.

There was little evidence of the shooting this morning, other than a wisp of yellow police tape floating in the breeze.

The neighborhood is poor, and there is significant drug and gang activity in the area. It is occasionally the scene of turf wars. The shooting occurred at the southern end of the housing projects.

Residents were reluctant to talk about the incident. A half-dozen police cars slowly cruised the area.

Officers said they knew little about the killing, but were on hand to try to prevent any further violence or retaliation.