China's space lab Tiangong-1 was tracked on radar -- Photo: FRAUNHOFER

It re-entered the atmosphere around 00:15 GMT on Monday, China's Manned Space Engineering Office said.

Tiangong-1 was launched in 2011 to carry out docking and orbit experiments.

It was part of China's efforts to build a manned space station by 2022, but stopped working in March 2016.

What do we know about where it came down?

The rather vague "above the South Pacific" is the line from space officials.

US specialists at the Joint Force Space Component Command said they had used orbit analysis technology to confirm Tiangong-1's re-entry.

Astronomer Jonathan McDowell, from the Harvard-Smithsonian Center for Astrophysics, tweeted that it appeared to have come down north-west of Tahiti.

Experts had struggled to predict exactly where the lab would make its re-entry - and China's space agency wrongly suggested it would be off Sao Paulo, Brazil, shortly before the moment came.

The European Space Agency said in advance that Tiangong-1 would probably break up over water, which covers much of the Earth's surface.

It stressed that the chances of anyone being hit by debris from the module were "10 million times smaller than the yearly chance of being hit by lightning".

It's not clear how much of the debris reached the Earth's surface intact.

Why did the space lab fall like this?

Ideally, the 10m (32ft)-long Tiangong module would have been taken out of orbit in a planned manner.

Traditionally, thrusters are fired on large vehicles to drive them towards a remote zone over the Southern Ocean. This option appears not to have been available after the loss of command links.

Thirteen space agencies, under the leadership of the European Space Agency, used radar and optical observations to follow Tiangong's path around the globe.

Is this the biggest space hardware to fall out of the sky?

Tiangong was certainly on the large size for uncontrolled re-entry objects, but it was far from being the biggest, historically:

 The US space agency's Skylab was almost 80 tonnes in mass when it came back partially uncontrolled in 1979. Parts struck Western Australia but no-one on the ground was injured
 Nasa's Columbia shuttle would also have to be classed as an uncontrolled re-entry. Its mass was more than 100 tonnes when it made its tragic return from orbit in 2003.

Again, no-one on the ground was hit as debris scattered through the US states of Texas and Louisiana

Astrophysicist Jonathan McDowell believes Tiangong is only the 50th most massive object to come back uncontrolled.

China has launched a second lab, Tiangong-2, which continues to be operational. It was visited by a re-fuelling freighter, Tianzhou-1, just last year.

China's future permanent space station is expected to comprise a large core module and two smaller ancillary modules, and will be in service early in the next decade, the Asian nation says.

A new rocket, the Long March 5, was recently introduced to perform the heavy lifting that will be required to get the core module in orbit.

Source: BBC