FERGUSON, Mo. — The National Guard arrived in Ferguson but kept its distance from the streets where protesters clashed again with police, as clouds of tear gas and smoke hung over the St. Louis suburb where Michael Brown was fatally shot by a police officer.

Protesters filled the streets after nightfall Monday, and officers trying to enforce tighter restrictions at times used bullhorns to order them to disperse. Police deployed noisemakers and armored vehicles to push demonstrators back. Officers fired tear gas and flash grenades.

Capt. Ron Johnson of the Missouri Highway Patrol, who is in charge of security in Ferguson, said bottles and Molotov cocktails were thrown from the crowd and that some officers had come under heavy gunfire. At least two people were shot and 31 were arrested, he said. He did not have condition updates on those who were shot. Johnson said four officers were injured by rocks or bottles.

Demonstrators no longer faced the neighborhood’s midnight-to-5 a.m. curfew, but police told protesters that they could not assemble in a single spot and had to keep moving. After the streets had been mostly cleared, authorities ordered reporters to leave as well, citing the risk from the reported gunfire.

A photographer for Getty Images was arrested while covering the demonstrations and later released. Two German reporters were arrested and detained for three hours. Conservative German daily Die Welt said correspondent Ansgar Graw and reporter Frank Herrmann, who writes for German regional papers, were arrested after allegedly failing to follow police instructions to vacate an empty street. They said they followed police orders.

Johnson said members of the media had to be asked repeatedly to return to the sidewalks and that it was a matter of safety. He said in some cases it was not immediately clear who was a reporter but that once it was established, police acted properly.

Citing “a dangerous dynamic in the night,” Johnson also urged protesters with peaceful intent to demonstrate during the daytime hours.

The latest clashes came after a day in which a pathologist hired by the Brown family said the unarmed black 18-year-old suffered a bullet wound to his right arm that may indicate his hands were up or his back was turned. But the pathologist said the team that examined Brown cannot be sure yet exactly how the wounds were inflicted until they have more information.

Witnesses have said Brown’s hands were above his head when he was repeatedly shot by an officer Aug. 9.

The independent autopsy determined that Brown was shot at least six times, including twice in the head, the family’s lawyers and hired pathologists said.