Three young men were killed and a fourth wounded in what police suspect was an attack by a notorious street gang.

Police were searching for five or six assailants that witnesses said shouted "Mara Salvatrucha" before opening fire Friday inside an apartment building in Prince George's County in suburban Washington. The Spanish words are the formal name of the Salvadoran street gang also known as MS-13, which traces its origins to Los Angeles in the 1980s.

The Washington Post reported Sunday that investigators believe the gang, which has been building influence in northern Virginia and Prince George's County, is responsible for the attack.

Police said there is no immediate indication that the victims were affiliated with gangs.

The victims were ages 19, 20 and 29. Two were from Montgomery County, Md., and a third was from Virginia.

The survivor, a 21-year old Prince George's County man, is recovering at a area hospital.