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.

Police boats combed the banks of the Potomac River on Friday, moving slowly under rainy skies and scanning the shoreline as investigators sought clues into the midair collision that killed 67 people and raised questions about air traffic safety around the nation’s capital.

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.