Investigators searching for wreckage from last week’s deadly midair collision between a US military Black Hawk helicopter and an American Airlines plane near Washington, DC, conducted an overnight scan of the Potomac River where the aircraft fell using advanced imaging technology to map the riverbed and locate debris.

Salvage crews have recovered the last large pieces of aircraft wreckage from the Potomac River on Thursday and are focusing on collecting small pieces from the crash site where 67 died.