The large Chinese rocket Long March 5B is set to make an uncontrolled reentry back into Earth's atmosphere, but it is not yet clear exactly where or when the debris will hit the planet.
The rocket is "unpredictably" falling back to Earth after launching a part of the new T-shaped Chinese space station on Thursday local time in Wenchang, according to SpaceNews.
The 22.5-metric-ton Tianhe space station module is in its correct orbit after separating as planned from the core stage of the rocket, which is now expected to re-enter in a few days or about a week.
"It will be one of the largest instances of uncontrolled reentry of a spacecraft and could potentially land on an inhabited area," SpaceNews said.
The more likely possibility is the core stage will fall in an uninhabited place like Earth's oceans, which cover 70% of the planet.
The odds of a particular individual being hit by space debris are exceedingly low, once estimated at 1 in several trillion.
The launch of the first module of China's new space station called "Heavenly Palace" underlined how far the country has come in achieving its space dream.
The Tianhe core module houses life support equipment and a living space for astronauts, and is another key step in Beijing's grand plans to establish a permanent human presence in space.
Beijing has poured billions into its military-run space programme, with hopes of having a crewed space station by 2022 and eventually sending humans to the Moon.
The country has come a long way in its race to catch up with the United States and Russia, whose astronauts and cosmonauts have decades of experience in space exploration.
But Beijing sees its space project as a mark of its rising global stature and growing technological might.