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

NASA's Joint Space Operations Center in California said the agency is still trying to determine exactly when the Upper Atmosphere Research Satellite re-entered the atmosphere.

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 a path more than 800 kilometers long.

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 any collision with the International Space Station. The satellite is the largest piece of space debris to fall to the planet since NASA's Skylab space station crashed in western Australia 32 years ago.