SAN FRANCISCO (KRON)—A United Airlines flight landed safely back at San Francisco International Airport Monday afternoon because of an engine problem.

Flight 837 left the airport around 11:40 a.m. with 231 people on board, said FAA spokesman Ian Gregor.

The flight was on its way to the Narita International Airport near Tokyo.

One of the four engines of the plane has been shut down, according to SFO spokesman Doug Yakel.

The plane made a safe landing around 1:40 p.m.

The FAA is investigating what caused the engine problem.

The inboard engine on the left side of the plane was the one that caused the issue, Gregor said.Stay with KRON4 News for updates on air, online and on our mobile app.