A second worker remains seriously injured after 20 m fall from work platform at Heathrow site yesterday afternoon.

A Laing O’Rourke worker died and another was seriously injured in an accident on the Heathrow T5 site yesterday afternoon.

The workers fell about 20 m from a work platform on a multistory car park under construction at the T5 site. An investigation is underway into the incident, and construction across the site has stopped.

Both men were taken to Charing Cross hospital after the incident. Mathew Gilbert, a 27-year old from Plymouth, was pronounced dead last night. The unnamed second worker remains in a serious condition.

Work has been suspended in the area where the accident happened to enable investigations by the Health and Safety Executive, BAA and Laing O'Rourke. The T5 site has been closed today in a mark of respect to the men and their families.

Laing O'Rourke chairman Ray O'Rourke said: "This is a dreadful event and our thoughts are with the families and friends of both men. We take the safety of our workforce extremely seriously and we have initiated an immediate investigation. We are offering our full support and cooperation to the HSE." O'Rourke added that it was too early to speculate on the cause of the accident.

The T5 project is recognised as setting safety standards well above the industry average, and before yesterday's events had experienced no fatalities since construction began in 2002. T5 managing director Tony Douglas said he was "deeply shocked and saddened" by the accident, and said he was determined to understand the cause as soon as possible.