The U.S. space agency says pieces of a decommissioned satellite have fallen back to Earth over the Pacific Ocean.

NASA says it may never be known exactly when or where the pieces of the Upper Atmosphere Research Satellite fell, but it is most likely at the bottom of the Pacific Ocean.

NASA has said the risk to public safety from the falling debris was very remote. The space agency warned people not to touch any of the debris, which could be scattered along an 800-kilometers path.

NASA launched the research satellite in 1991 on a three-year mission to study ozone levels in the atmosphere. NASA took it out of service in 2005.

The satellite was placed into a lower orbit to avoid collision with the International Space Station. The satellite is the largest piece of NASA space debris to fall since the Skylab space station crashed 32 years ago in western Australia.