Two reporters briefly detained near protest in Ferguson, Mo.

Reporting from Ferguson, Mo. —  As police in this St. Louis suburb turned out in force Wednesday evening to discourage another night of unrest, they unleashed a brief contretemps by arresting a pair of reporters.

Protests have occurred every night since a Ferguson police officer fatally shot a young black man on Saturday. The reporters were among those who came to Missouri to cover the shooting and its aftermath.

Wesley Lowery of the Washington Post and Ryan J. Reilly of the Huffington Post were taken into custody in a McDonald’s restaurant near a demonstration.

The action appeared to catch Ferguson Police Chief Thomas Jackson by surprise.

“Oh, God,” he told the Los Angeles Times when he learned what had happened. Then Jackson called the St. Louis County Police Department, which was heading the command Wednesday night.

“I told them to release them,” Jackson told The Times.

Lowery and Reilly were set free shortly thereafter. The chief said his staff had been unaware of the arrests until notified by a reporter.

Jackson said both Reilly and Lowery had interviewed him earlier in the day and had asked thoughtful questions. He said whoever arrested them was “probably somebody who didn’t know better.”

Lowery and Reilly tweeted that they were in a McDonald’s near a demonstration when police came inside and asked patrons to leave.

“Officers slammed me into a fountain soda machine because I was confused about which door they were asking me to walk out of,” Lowery tweeted after his release. “Was waiting to be taken away, large black man SCREAMING for help in back of police truck. They refused his calls for paramedics. ‘I’m dying. I’m dying. Please call help’ he screamed. They mocked him.”

Lowery said he was released without paperwork or explanation.

Since the unrest began Saturday night, dozens of protesters have been arrested and one has been critically wounded by gunfire. At least 10 more people were arrested later Wednesday night as the unrest continued.

Gov. Jay Nixon tweeted that he was canceling planned appearances to visit the area Thursday. He added: “Closely monitoring situation.... Ask for calm & urge law enforcement to respect rights of residents & press.”

After his release, Lowery told MSNBC’s Rachel Maddow that the officers who detained him appeared to think he wasn’t leaving McDonald’s fast enough.

He was gathering his things and preparing to leave when his bag slipped off his shoulder, he said, so he told officers he would adjust his bag. Then, Lowery told Maddow, the officers said, “Let’s take him,” forcibly removing him and putting him in temporary restraints.

“I was never looking to get arrested,” Lowery said. “I don’t believe Ryan and I did anything to warrant getting arrested.”

Washington Post Executive Editor Martin D. Baron said “there was absolutely no justification” for Lowery’s arrest and called the police conduct appalling.

“He was illegally instructed to stop taking video of officers,” Baron said in a statement. “Then he followed officers’ instructions to leave a McDonald’s — and after contradictory instructions on how to exit, he was slammed against a soda machine and then handcuffed. That behavior was wholly unwarranted and an assault on the freedom of the press to cover the news. The physical risk to Wesley himself is obvious and outrageous.

“After being placed in a holding cell, he was released with no charges and no explanation. He was denied information about the names and badge numbers of those who arrested him. ... We are appalled by the conduct of police officers involved.”

@mattdpearce

Times staff writers James Queally, Julie Westfall, Lauren Raab and Ryan Parker contributed to this report.