NASA officials say pieces of a dead satellite the size of a school bus will fall to Earth around Sept. 23.

Officials said the odds of the Upper Atmosphere Research Satellite striking someone are about one in 3,200.

Nevertheless, NASA is watching the six-ton satellite closely.

"Even as we get to the final orbits we don't know where along that path it's going to come in, and that covers a tremendous amount of land," Dr. Mark Matney, with the Johnson Space Center, said.

Most of UARS is expected to burn up in the atmosphere, but experts estimate about 26 pieces of metal debris will fall to the Earth over a stretch of 400 to 500 hundred miles.

The heaviest piece of debris is expected to weigh about 350 pounds.

"If you find something you think may be a piece of UARS, do not touch it," NASA officials warned. "Contact a local law enforcement official for assistance."