Investigators trying to determine what caused last week’s deadly midair collision between a US military Black Hawk helicopter and an American Airlines plane near Washington, DC, briefed lawmakers Thursday on what they’ve learned after combing through data from both aircraft and air traffic control.

The Unified Command said all 67 victims of the American Airlines and Black Hawk helicopter collision have been recovered and identified.

A key safety system was turned off on a U.S. Army helicopter that collided with an American Airlines regional jet last week near Washington Reagan Airport, killing 67.