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

The U.S. National Transportation Safety Board said on Monday it is investigating a United Airlines flight on Friday from Lagos, Nigeria to Washington D.C., in which a sudden aircraft movement led to injuries of passengers and cabin crew.

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.