Malaysia’s transport minister on Thursday vowed to take stern action against an air traffic control supervisor if it is confirmed that he was asleep on the job when Malaysia Airlines Flight 370 disappeared a year ago.

An interim investigation report last Sunday contained transcripts of conversations between air traffic controllers in the region and the airline that revealed confusion in the hours after the Boeing 777 dropped off radar with 239 people aboard while flying from Kuala Lumpur to Beijing.

In one conversation four hours after the plane disappeared, a Kuala Lumpur air traffic controller told a Malaysia Airlines official that he would need to wake up his supervisor when pressed on the exact time of the last contact with the plane. The controller came on duty after the plane vanished.

Transport Minister Liow Tiong Lai said his department viewed the matter seriously and was conducting an internal probe.

“The work is on rotation. … If he is on a working shift, this is serious. We will definitely take action if there is any misconduct,” he told reporters.

Liow said the ministry didn’t investigate the matter earlier as they were waiting for Sunday’s report by the independent safety investigation team.

The ministry’s probe will be “very fast,” he added, without saying when it would be completed.

Despite an exhaustive search in the southern Indian Ocean where the plane was believed to have crashed based on analyses of transmissions between the aircraft and a satellite, no trace of wreckage has been found. In late January, Malaysia’s government formally declared the plane’s disappearance an accident and said all those on board were presumed dead.

The report Sunday also showed that the battery of the underwater locator beacon for the plane’s data recorder had expired more than a year before the jet vanished March 8, 2014, because of a computer data error and went unnoticed by maintenance crews.

Australian Prime Minister Tony Abbott has said the hunt for the plane would continue even if searchers scouring a 60,000-square-kilometer (23,166-square-mile) swath of the seabed off Australia’s west coast do not find it by May.

Liow said a tripartite meeting involving ministers from Australia, Malaysia and China – where most of the passengers are from – would take place in Kuala Lumpur next month to discuss the next step. SAPA