Harvard astrophysicist Jonathan McDowell, who tracked the tumbling rocket part, said on Twitter: “An ocean re-entry was always statistically the most likely. It appears China won its gamble … But it was still reckless.”
China’s official Xinhua News Agency said re-entry occurred at 7.24 pm local time on Saturday.
“The vast majority of items were burned beyond recognition during the re-entry process,” the report said.
Despite that, NASA administrator Bill Nelson issued a statement saying: “It is clear that China is failing to meet responsible standards regarding their space debris.”
Usually, discarded rocket stages re-enter the atmosphere soon after liftoff, normally over water, and do not go into orbit.
The Long March 5B rocket carried the main module of the new Chinese space station Tianhe, or Heavenly Harmony, into orbit on April 29.
The uncontrolled return of the rocket led to criticism from the US and Europe over fears it could land in a populated area - although the chances were very low.
China plans 10 more launches to carry additional parts of the space station into orbit.
China’s first space station, Tiangong-1, crashed into the Pacific Ocean in 2016 after Beijing confirmed it had lost control.
In 2019, the space agency controlled the demolition of its second station, Tiangong-2, in the atmosphere.
In March, debris from a Falcon 9 rocket launched by US aeronautics company SpaceX fell to Earth in Washington and on the Oregon coast.
China was heavily criticised after sending a missile to destroy a defunct weather satellite in January 2007, creating a large field of hazardous debris imperilling satellites and other spacecraft.