DUBLIN (Reuters) - One person died and three were missing after a Sikorsky S-92 helicopter crashed off the coast of Ireland during a rescue operation, the Irish Coast Guard said on Tuesday.

The search-and-rescue helicopter, which was assisting another aircraft with a medical evacuation from a fishing vessel, lost contact at around 0100 GMT, it said in a statement.

A spokesman for U.S.-based Sikorsky, part of Lockheed Martin, said the firm was working with the helicopter’s operator to gather information on the possible cause of the crash.

Sikorsky in January issued a service notice saying the tail rotor and bearing assemblies of the S-92 should be checked following an incident with the tail rotor during a landing on a rig off Scotland on Dec. 28.

European regulators last year grounded certain Super Puma helicopters made by rival Airbus after an accident in which the rotor head separated from the helicopter.

The Super Puma ban was conditionally lifted by the European safety agency but Britain and Norway have kept national restrictions in place.