"There is no need for people to worry about its re-entry into the atmosphere," an article by the China Manned Space Engineering Office published on state media said.
"It won't crash to the Earth fiercely, as in sci-fi movie scenarios, but will look more like a shower of meteors."
As of Thursday, the space lab is orbiting the Earth at a height of 196.4 kilometers (122 miles).
Witnesses may see 'series of fireballs'
Markus Dolensky, technical director of the International Center for Radio Astronomy Research in Australia, said witnesses to the Tiangong-1 descent should see "series of fireballs" streaking across the sky -- provided there were no clouds.
"It is now nearing its fiery demise as it gradually gets slowed down by the fringes of the Earth's upper atmosphere," he said.
While it is not uncommon for debris such as satellites or spent rocket stages to fall to Earth, large vessels capable of supporting human life are rarer.
The re-entry latitude of the Tiangong-1 is expected to be within 43 degrees north and 43 degrees south of the equator, a huge swath of the earth which stretches from New York to Cape Town. Scientists say it's not possible to be more specific about exactly where it will come down.
"Some parts of the upper atmosphere are thicker than others meaning the craft slows unpredictably and since it travels around the Earth in just 90 minutes even an uncertainty of a two minutes means the craft could fall anywhere along a 1,000 kilometer track," Alan Duffy, a research fellow in the Center for Astrophysics and Supercomputing at Swinburne University of Technology in Australia, said.