The American space agency NASA says a six-tonne satellite has plunged through the atmosphere, breaking up and possibly scattering debris in Canada.
There are reports on Twitter of debris falling over Okotoks, a town south of Calgary in western Canada, most likely the remains of the Upper Atmosphere Research Satellite (UARS) which had been in orbit for 20 years.
Scientists were unable to pinpoint the exact time and place where the remains would return to Earth due to the satellite's unpredictable tumbles as it ploughed through the upper atmosphere.
NASA says it was the biggest piece of United States space junk to fall in 30 years.
The US space agency had stressed there was a "very remote" risk to the public from the 26 fragments of the Upper Atmosphere Research Satellite (UARS) that were expected to survive the fiery re-entry into the atmosphere.
UARS was launched in September 1991 and was decommissioned in December 2005 when it ran out of fuel.
In 1979, debris from the 77-tonne SkyLab, another satellite that plunged to Earth, was scattered over parts of Western Australia.
