A United Airlines flight had to make an emergency landing in Lagos, Nigeria due to a midair incident causing loss of pressure and sharp descents.

It is unclear what caused the jolt; United Airlines has said the cause was not severe turbulence, and that it is “working with aviation authorities in the US and Nigeria to understand the cause.”

A United Airlines flight from Africa to Washington D.C. had to turn around on Thursday after a "technical issue" caused "unexpected aircraft movement," the airline said.