Federal investigators say an Atlanta police helicopter hit the top of power line pole and its support cables before it crashed on a busy city street, killing two officers on board.

No one on the ground was injured. The officers were searching for a 9-year-old boy who had run away from home. He was later found unharmed.

NTSB investigator Ralph Hicks said Sunday witnesses heard the helicopter and saw a flash of light when it hit the pole. He says part of the chopper's landing gear was caught in the support cables and the power company had to help authorities get it down.

Hicks said investigators are trying to figure out why the helicopter crashed. He said they hope to have a preliminary report later this week.

Meanwhile, mourners are leaving flowers, cards and other mementos at a makeshift memorial near the site of the crash.

A trust fund has been established for the families of the officers, 48-year-old pilot Richard J. Halford of Lithia Springs; and 40-year-old tactical flight officer Shawn A. Smiley, 40, of Lithonia. Wells Fargo bank officials say they will start taking donations at noon on Monday for the trust funds.

Tags: crash, National Transportation Safety Board, helicopter crash, ntsb