On Tuesday, the Wall Street Journal reported that US investigators believe someone intentionally brought down a China Eastern flight in March, China's most significant flying accident in decades.

On March 21, China Eastern flight MU5375 was en route from Kunming to Guangzhou when it mysteriously plummeted from 9000 feet into a mountainside, killing all 132 aboard.

The site's so-called black box flight data recorders were taken to the United States for analysis.

According to Wall Street Journal, which cited sources involved with the investigation, this data indicates that someone — potentially a pilot or a person who had forced their way into the cockpit — sent commands to send the Boeing 737-800 into a plunge.

The Journal quoted "a person familiar with American officials' preliminary assessment" as adding, "The plane did what it was instructed to do by someone in the cockpit."

The newspaper reported that US officials feel their finding is supported because Chinese investigators have not yet identified any issues with the aircraft or flight controls that could have caused the crash and need to be fixed for future flights.

Tuesday, both the US National Transportation Safety Board and Boeing declined to comment to AFP over the probe.

China's Civil Aviation Administration (CAAC) stated in April that according to a report from Boeing, inspectors found no indication of "anything abnormal."

The CAAC said that employees had completed safety criteria before takeoff. The plane was not carrying hazardous materials, and it did not appear to have encountered bad weather, but a comprehensive inquiry may take years.

China's ruling Communist Party responded swiftly to regulate information in the early aftermath of the crash, firing up the censorship machine as media outlets and residents rushed to the crash scene.

It has retained a firm grip on the story, with the preliminary investigation failing to answer crucial points.

After the catastrophic collision near the southern city of Wuzhou, police quickly roped off a broad area, and China's internet regulator stated that it had wiped vast volumes of "illegal information" about the crash from China's heavily regulated internet.

A social media hashtag with the flight number appears to have been deleted.

China's usually stellar air safety record was marred by the crash, the deadliest in almost 30 years.