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.

Police boats have returned to the Potomac River as part of the recovery and investigation after the United States’ deadliest aviation disaster in almost a quarter century. Law enforcement officials told The Associated Press that more than 40 bodies have been pulled from the river as the massive recovery effort continues Friday.