Updated 7.27am

ONE MAN HAS died after apparently being overcome with fumes while working on a drainage system in Portmarnock, north Dublin.

A second man is critically injured and in hospital.

Initial reports said that two men had died, but the latest information from the Dublin Fire Brigade is that one man was killed and one critically injured.

Source: Eamonn Farrell/Photocall Ireland

The two, who were employees of Draintech – a drain-clearing and service firm – were working on a sewerage pipe at Drumnigh Wood when the incident occurred.

Speaking to RTÉ’s Six One, third officer with Dublin Fire Brigade Gerry Stanley said routine maintenance was being carried out:

One of these people got into difficulty in the sewer and collapsed into the pit. An attempt was made to assist him by one of his colleagues, who also got into difficulty.

Source: Eamonn Farrell/Photocall Ireland

Three firefighters who attended the scene also became ill and have been taken to hospital as a precaution. One suffered a facial injury while recovering the first fatality.

Stanley confirmed that all three have now been discharged.

A spokesperson for the Health and Safety Authority confirmed the fatality and said an investigation is underway.

Dublin Fire Brigade said that three ambulances, three fire engines, and an advanced paramedic responded “very quickly” to the incident. Those injured were taken to Beaumont Hospital.

My thoughts with those involved in an industrial accident in #Portmarnock this afternoon. Two fatalities reported. Emergency crews on scene. — Alan Farrell TD (@AlanFarrell) June 10, 2015 Source: Alan Farrell TD /Twitter

- Additional reporting Daragh Brophy and Nicky Ryan

An earlier version of this story said that two men had died. This followed incorrect information provided by investigating authorities.