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.

United Airlines said it was cooperating with U.S. and Nigerian investigators to determine what exactly happened on the flight.

The authorities in Nigeria said that the United Airlines plane had to return to Lagos, Nigeria, after the episode. Six people were treated at a hospital, officials said.

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 jet was forced to make an emergency landing after plummeting mid-air following take-off. At least six people were injured after the plane jolted during the flight from Nigeria on Friday. The flight, which was heading from Lagos to Washington DC, had 245 passengers and 11 crew on board at the time.

In an update, Nigerian officials said an additional 27 passengers and 5 crew members suffered minor injuries in the incident. In all, 38 were hurt.

The flight was diverted shortly after take-off due to a mid-air jolt which has injured several people - we'll be bringing you the latest updates, pictures and video on this breaking story

United spokesperson Leslie Scott confirmed that all six injured had since been released from hospital, the Mirror reports. The same flight was also diverted on Tuesday, January 21, with data also revealing a rapid drop in altitude of 1,000ft at around 89 minutes after take-off. It has not been determined whether the two incidents are connected/