The National Transportation Safety Board is examining new data that may indicate the Black Hawk helicopter involved in a fatal midair collision with American Airlines Flight 5342 near Washington, D.C.

Victims' families gathered near the site where a plane and copter collided and fell into the Potomac River. 'They are all hurt,' an official said.

This data point is one of several key mysteries investigators are exploring as they seek to explain what caused the nation's worst air disaster in more than a decade, aviation experts said.