FERGUSON, Mo. — The police conducted a manhunt in this tense and battered city on Thursday in search of whoever shot two police officers as they worked at a protest after the resignation of the chief.

The shooting just after midnight on Thursday morning, described as “really an ambush” by Chief Jon Belmar of the St. Louis County Police Department, was denounced by all sides in the continuing conflict over law enforcement here after the death, at the hands of the police, of an unarmed black teenager last summer, and the police crackdown on the ensuing protests.

By Thursday night, relative calm had returned to the streets as clergy members and activists gathered for a candlelight prayer vigil that paired condemnations of the officers’ shootings with support for nonviolent protests. About 100 protesters later marched outside the Ferguson Police Department, but by midnight, with a light rain falling, most of the demonstrators had cleared the way, and the streets were largely quiet. The police said no one had been arrested — neither protesters, nor suspects.

Earlier, police SWAT units surrounded a house a few blocks from the scene of the shooting, and officers climbed onto the roof and broke through a vent to gain access. The police took in three people from the house for questioning and released them hours later.