(CNN)Police have been in an hourslong standoff with at least one barricaded suspect who they say shot six officers on Wednesday in a North Philadelphia neighborhood.

Two officers were trapped inside the row house, Philadelphia Police Commissioner Richard Ross Jr. told reporters.
Sgt. Eric Gripp, a police spokesman, tweeted about five hours after the standoff began that SWAT had evacuated the officers. Gripp said the shooter was still barricaded inside.
Negotiators were trying to communicate with the shooter, but the gunman only picks up the phone without answering, Ross said Wednesday night.