HOUSTON -

A bomb threat was found in a restroom on a flight from Houston.

The threat was found on a United Airlines plane headed to London on Saturday.

Sources told KPRC Local 2 that the note was discovered when the plane was over the Atlantic Ocean and about four hours away from London's Heathrow Airport.

Someone wrote the note on the wall of a restroom in the front of the plane, officials said.

When the flight landed, the plane was pulled over to a side runway. Passengers and crew members were taken off the plane and screened.

Police and bomb-sniffing dogs searched the plane for about four hours. No explosive devices, real or fake, were found.

The Transportation Safety Administration is investigating the incident. No suspects have been identified.