The influential US Wall Street Journal reported on Tuesday, citing a source close to the matter about the initial assessment of US officials.
A Western official told Reuters that a preliminary investigation had found no indication of a technical error and was focusing on the aircraft’s crew.
The aircraft manufacturer Boeing declined to comment.
They advised Chinese aviation regulators to ask questions. The U.S. National Transportation Safety Board (NTSB) did not immediately return calls seeking comment.
In March, a Boeing 737-800 of China Eastern Airlines crashed in the mountains of Guangzhou after a sudden landing. It was going from Kunming to Guangzhou.
The 123 passengers and nine crew members on board were killed.
It was the deadliest plane crash on mainland China in 26 years.