Updated

Ireland has mounted a major search off the County Mayo coast after a sea rescue helicopter with four crew members crashed overnight in the Irish Sea.

Coast Guard director Eugene Clonan says one crew member has been found and is hospitalized in critical condition, while hopes are fading of finding the other three personnel following Tuesday's crash.

The Dublin-based Sikorsky helicopter disappeared from radar before 1 a.m. (0100 GMT) as it arrived in Mayo to support a second helicopter in rescuing an ill fisherman aboard a British trawler.

Searchers have reported finding helicopter debris in the water 8 kilometers (5 miles) from the nearest helicopter refueling point beside Mayo's Blacksod lighthouse.

Tuesday's search involves an Irish naval vessel, two lifeboats, five private trawlers, two helicopters and an army surveillance plane.