A GRIM accident warning was issued today after horrified children saw a worker killed in a theme park rollercoaster tragedy.

The Health and Safety Executive has launched an investigation following the incident which killed Harold Mathews, 59, at the Camelot theme park near Chorley yesterday.

Today, as bosses expressed their sorrow for his family and a fellow worker spoke about staff's shock, a spokesman for the Royal Society for the Prevention of Accidents, RoSPA, said: "This accident should serve as a warning to all fairground operators that things can go wrong, even if all the correct checks have been carried out."

In the last year there have been five fatalities on fairgrounds, and just 14 in the 12 years before that.

The spokesman added: "They are becoming more common. This could be because the rides are getting faster and higher. We have concerns because theme parks seem to be going all out to better each other every time.

"Although still relatively few, the number of accidents has prompted the Health and Safety Executive to set up a rides working group and we are waiting to see what their conclusions are."

Mr Mathews, of Wigan, is believed to have been hit by the new Gauntlet rollercoaster. The park was closed today as a mark of respect.

Emergency services were called to the park, at Charnock Richard, at about 2pm.

A post mortem examination has been carried out to try to establish the exact cause of death and Mr Mathews' family have been informed.

A police spokesman said the exact circumstances of the accident were still unclear and it was not known whether Mr Mathews had been struck by the rollercoaster.

The Gauntlet was a ride unveiled earlier this year as part of the park's Land of the Brave, which contains several white-knuckle rides.

Staff described it as an overhead rollercoaster which includes a loop.

The member of staff, who asked not to be named, said: "We couldn't believe it when people started saying what had happened.

"Children actually saw what happened. It has been such a brilliant year and we all know each other, at least to smile to anyway. It is so sad."

Roy Page, chief executive of Camelot Theme Park, said: "I can confirm that an incident occurred that resulted in a fatality involving a member of staff.

"We are all devastated and extremely distressed and our thoughts and condolences are with the colleague's family at this time."

A spokesman for the Health and Safety Executive confirmed they were investigating.

Camelot, which is based on the legend of King Arthur, is one of the country's biggest theme parks with more than 100 rides and attractions and draws visitors from throughout the country. It is famous for its medieval jousting displays and children's farm which attract just under a million visitors each year.

The Camelot and Park Hall site covers 140 acres and employs more than 400 people. It was bought by the Granada Group in 1986 in a £6million deal. In recent years it has invested a further £4.5million in the site.

It was named best North West visitor attraction in 1999.

Mr Page added: "People who witnessed this incident are being looked after and have been offered counselling.

"We will re-open on Wednesday but we do not know at this stage which rides will be open."