U.S. President Barack Obama and Attorney General Eric Holder condemned the attack on the officers, who were treated at a local hospital and released, as a law enforcement team in tactical gear swarmed a home in the St. Louis suburb. Television images showed officers on the roof breaking into the attic with heavy tools.

Shawn McGuire, a St. Louis County police spokesman, said an undisclosed number of people were taken from the house but there have been no arrests so far. He would not confirm media reports that two men and a woman were led away.

Long-simmering tensions between African-Americans and Ferguson's mostly white police force came to a boil in August when a white policeman killed an unarmed black teenager. The shooting of 18-year-old Michael Brown led to a coast-to-coast wave of demonstrations last year.