The space station will burn up as it enters the atmosphere but there are chances that some small pieces of the station will survive the burning process of re-entry and will strike the planet.
Once it enters Earth's atmosphere, the vast majority of the craft will vaporize, causing it to light up skies like a shooting star on steroids.
Launched in 2011, Tiangong-1 was China's first space station, and was intended as a training platform for a much larger space station scheduled to launch in the 2020's.
CHINA'S first space station with "highly toxic" chemicals on board is expected to crash down to Earth within weeks - but experts can not say where the 8.5 tonne spacecraft will hit.
"Remember that a 1 hour error in our guessed reentry time corresponds to an 27000 km (17000 mile) error in the reentry position", he said in a tweet.
The scientist also dismissed reports from a "news" website that there was a risk that Tiangong-1 would land in Thailand and that cancerous hydrazine, the propellant it carries, would spread.
Aerospace in a statement said that there was "a chance that a small amount of debris" from the module will survive re-entry and hit the Earth. "To become affected, a person must touch or inhale it in large quantities for a long period", he said. Aboard the station there is a supply of highly toxic fuel.
In any case, he said, his agency was coordinating closely with worldwide peers and they have asked China how much hydrazine was left in the spacecraft. We know that the space station is coming down, we just don't know when or where.
Tiangong-1 is expected to pass over Thailand on March 16, when a Gistda team will observe it from Doi Inthanon, the country's highest mountain, in Chiang Mai. The current estimated window is "highly variable", the European Space Agency cautioned.
The doomed 8.5-tonne craft, which has been hurtling towards Earth since control was lost in 2016, is believed to contain unsafe hydrazine.
China's Shenzhou-9 manned spacecraft, left, conducts docking with the Tiangong-1 space lab module on Monday, June 18, 2012. The delay of re-entry into the earth's atmosphere, which Beijing said would happen in late 2017, had led some experts to suggest the space laboratory may be out of control.
"In the history of spaceflight, no known person has ever been harmed by reentering space debris", the Aerospace Corp. stated in January.
In recent months, the spacecraft has been speeding up and it is now falling by around 6km (3.7 miles) a week.
Holger Krag, head of ESA's Space Debris Office, said: 'Owing to the geometry of the station's orbit, we can already exclude the possibility that any fragments will fall over any spot further north than 43°N or further south than 43°S.
In 2016, China admitted that it had lost control of Tiangong-1 and would be unable to perform a controlled re-entry.