A United Airlines flight from Newark to Spain was forced to turn back midair on Saturday after reports of a Bluetooth device with a suspicious four-letter word.

The FBI and police responded to reports of a security concern with an unruly passenger on the plane, which diverted to Dane County Regional Airport.

The flight to Palma de Mallorca diverted back to Newark late on Saturday. Air traffic audio and social media posts indicate an onboard Bluetooth device raised security concerns.