Military authorities are still looking into what caused part of an Air Force plane to break off and crash in the backyard of a San Antonio, Texas home on Thursday. 

Officials said the piece was from a Boeing C-17 that had undergone repair at a maintenance hanger at Port San Antonio and was on its way back to McChord Air Force Base in Washington.

No injuries

The part fell from the sky and landed in the backyard of Nate Martinez around noon on Thursday. No one was injured.

'A loud thud'

'There was just a hard scraping sound and a loud thud," said Martinez. Neighbors said they heard a 'clinking and clanking sound' and 'a popping noise', then saw the object falling from the sky.

The crash knocked out power in the neighborhood for about four hours.