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.

The National Transportation Safety Administration says the Army Black Hawk helicopter that collided with an American Airlines jet over the Potomac River last Wednesday was flying at about 300 feet at the time of the collision,