Indonesia’s Transportation Ministry said on Saturday, January 9 that it had lost contact with a passenger jet after it took off from the capital, Jakarta, and flew over the Java Sea, The New York Times reports.

The ministry said that the last contact with the plane, Sriwijaya Air Flight 182, was made at 2:40 p.m. local time. The Boeing 737-524 was bound for the city of Pontianak on the island of Borneo. More than 50 people were believed to be aboard.

Four minutes after taking off, the 26-year-old plane lost more than 10,000 feet of altitude in less than 60 seconds, according to Flightradar24, the flight-tracking service.

The aviation sector in Indonesia, a developing country of thousands of islands, has long been plagued by trouble, contending with poor safety records and the rapid growth of budget airlines.

In 2018, Lion Air Flight 610 plunged into the Java Sea with 189 people aboard after the 737 jetliner’s antistall system, designed by Boeing, malfunctioned.

The country’s aviation safety commission said it was on alert and that the transportation minister was on his way to the international airport in Jakarta. Patrol boats were heading to waters northwest of Jakarta where the plane was last seen, the Indonesian National Search and Rescue Agency said.