Officials have recovered the bodies of 55 of the 67 victims killed after an Army helicopter and an American Airlines passenger plane collided at low altitude near Ronald Reagan Washington National Airport last week.

“It’s my belief that we’re going to recover everyone,” said D.C. Fire Chief John Donnelly during a Sunday briefing on the victim recovery efforts and debris removal.

Divers are still searching the frigid Potomac River for the remains of 12 people. The waterway remains closed to unauthorized vessels.

All 64 people aboard AA Flight 5342 and all three people in the Black Hawk helicopter were killed the Wednesday night collision, the deadliest air crash to happen in the country in two decades.

The process of lifting the wreckage out of the river will start Monday.

“Our goal is to really lift as much as we can, given the fact that we are also accounting for the human remains component,” said Col. Francis Pera of the Army Corps of Engineers.

Meanwhile, the National Transportation Safety Board is leading the investigation into how the crash could have happened.

The NTSB said Saturday that the airplane — an inbound flight from Wichita approaching one of DCA’s three runways — was 325 feet in the air, give or take 25 feet, at the time of impact. Early information suggests the Army helicopter was flying above 200 feet, the maximum allowed altitude for the path it was on, according to the independent federal agency.

The helicopter was on a training mission, and investigators are working to confirm whether the crew had on their night vision while flying the clear, dark skies.

The collision has renewed concerns about the area’s level of air traffic congestion, which leaves little room for error in the airspace above major transport hubs that serve the nation’s capital region.