United flight diverted to London over reported medical emergency

Those who requested assistance have since been released, the airline said.

According to passenger Pete Teoh, several passengers had felt lightheaded. He tweeted a photo of EMTs on board the plane and emergency personnel outside.

Teoh said "sick passengers" were "being attended to" on a bus next to the plane.

The airline added, "We have provided customers meals, hotel accommodations and are working with customers to get them to their final destinations."