Officials say the conditions of the Potomac River are complicating recovery efforts of the bodies of the 67 presumed dead in a mid-air collision between American Airlines flight 5342 from Wichita and a military Black Hawk helicopter.

Tragedy struck in Washington, D.C. on Wednesday night, as an American Airlines jet collided with an Army Black Hawk helicopter. That crash resulted in the largest aviation disaster the United States has seen since November 2001.

Divers are expected to return to the Potomac River as part of the recovery and investigation after the United States’ deadliest aviation disaster in almost a quarter century