SEVEN sailors had to be airlifted to hospital after a chemical alert caused by a toilet cleaner.

The Royal Navy crew were left with eye and throat irritation after a gas was released when two cleaning agents were mixed together.

The crew were on the HMS Illustrious, 20 miles off the coast of Hartlepool, when a gas was released.

A shipmate cleaning a toilet, mixed together two cleaning agents which resulted in a chlorine-based vapour being released in the aircraft carrier.

Royal Navy bosses alerted a helicopter, from the base at RAF Boulmer, in Northumberland, which transported seven injured men to the James Cook University Hospital, in Middlesbrough, for treatment.

An investigation is now underway by the warship's bosses to find out exactly how the gas release occurred.

A Royal Navy spokeswoman said: "The ship was in the North Sea off the port of Hartlepool carrying out some exercises when the incident happened.

"Basically someone was routinely cleaning a toilet area and mixed up some cleaning chemicals which caused a vapour.

"Seven crew members were affected by that and as a precautionary measure they were flown by RAF helicopter to hospital."

She added: "The affected area on the ship has been scrubbed down and sanitized and the gas has been properly vented.

"As a matter of course the ship will carry out an investigation. This is the normal course of business."

The alert happened in the early hours of Wednesday.

A spokeswoman for James Cook hospital said: "The sailors had a medical check-up and were all discharged.

She said: "They were kept in during the night for precautionary measures due to the exposure to the chlorine-based gas."

On release from hospital the crew travelled to the ship's base port, Portsmouth, to re-join the vessel.