The Wall Street Journal is reporting that US investigators suspect a missing Malaysian jetliner flew on for four hours after it lost contact with air traffic controllers.

The suspicion is based on data from the plane’s engines that are automatically downloaded and transmitted to the ground as part of routine maintenance programs.

The report raises questions as to why the Boeing 777 was flying like that, and if anyone was in control during that time.

The plane’s last known confirmed position was roughly halfway between Malaysia and Vietnam.

Malaysian authorities have since said they tracked what could have been the plane changing course and heading west.

No signs of the missing Malaysian jetliner have been found at a spot where Chinese satellite images showed what might be plane debris, Malaysia’s civil aviation chief said Thursday, deflating the latest lead in the five-day hunt.

“There is nothing. We went there, there is nothing,” Azharuddin Abdul Rahman told reporters in Kuala Lumpur.

Vietnamese officials previously said the area had been “searched thoroughly” in recent days.

The hunt for the Boeing 777 has been punctuated by false leads since it disappeared with 239 people aboard just hours after leaving Kuala Lumpur for Beijing early Saturday. The plane was heading northeast over the South China Sea when it disappeared, but authorities believe it may have turned back and headed into the upper reaches of the Strait of Malacca or beyond.

The location where Chinese images showed possible debris is not far from where the last confirmed position of the plane was between Malaysia and Vietnam. The images and coordinates were posted on the website of China’s State Administration of Science, Technology and Industry for National Defense.

A Xinhua report said the images from around 11 a.m. on Sunday appear to show “three suspected floating objects” of varying sizes in a 20-kilometer radius, the largest about 24-by-22 meters (79-by-72 feet) off the southern tip of Vietnam.

Pham Quy Tieu, deputy transport minister, told The Associated Press that the area had been “searched thoroughly” by forces from other countries over the past few days. Doan Huu Gia, chief of air search and rescue coordination center, said Malaysian and Singaporean aircraft were scheduled to visit the area again Thursday.

Li Jiaxiang, chief of the Civil Aviation Administration of China, said later China had yet to confirm any link between the suspected floating objects and the plane.

Malaysia has come under some criticism for its handling of the search, which currently covers 35,800 square miles (92,600 square kilometers) and involves 12 nations.

Investigators have not ruled out any possible cause to explain the disappearance of the plane and the 239 people on board.

Copyright 2014 The Associated Press.