Police are locked in a lengthy stand-off with a gunman who injured at least six officers during a shootout in the US city of Philadelphia.
A gun battle broke out between police and a male shooter at around 16:30 local time (20:30 GMT).
The officers were serving a drugs warrant at a home in Philadelphia’s Nicetown-Tiago neighbourhood when the gunman opened fire.
Five hours on, Philadelphia Police say the suspect is yet to surrender.
Two officers are still believed to be trapped inside the home with the gunman, police said.
Police Commissioner Richard Ross said he was “worried about a potential hostage situation”.
“There’s no indication that he’s trying to surrender, we do know that he is still alive, there’s no question of that because of the shots that keep ringing out,” Commissioner Ross said in a news conference.
Officers were still “attempting to communicate with the shooter” and urging him to give himself up, police Sergeant Eric Gripp tweeted.
Six officers involved in the shootout were taken to hospital with non-life threatening injuries.
Mr Ross said “many of them had to escape through windows and doors” as the suspect fired.
Video from the scene shows dozens of police cars and officers outside the home where the gunman is hunkering down.
US President Donald Trump was briefed on the shooting, deputy White House press secretary Hogan Gidley said.