March 17 (Reuters) - The U.S. Department of Transportation is investigating the Federal Aviation Administration's approval of Boeing Co's 737 MAX jetliners, the Wall Street Journal reported on Sunday, citing people familiar with the probe.

The Transportation Department's inquiry was launched in the wake of October's Lion Air accident that killed 189 people and is being conducted by its inspector general, which has warned two FAA offices to safeguard computer files, the Journal said https://on.wsj.com/2Hrzvlq.

Boeing did not immediately respond to a request for comment. The Federal Aviation Administration declined to comment. Two government officials briefed on the matter said it would not be surprising for the Transportation Department’s inspector general to investigate a major safety issue but could not immediately confirm the report.

(Reporting by Ismail Shakil in Bengaluru)