By Jon Coates, PA News

TWO teenage girls are believed to have killed themselves in a bizarre suicide pact after attending a house party, police said today.

The bodies of the close friends were found slumped inside a car at a house in Crawley, West Sussex, yesterday morning. They had attended a party at the house of a 17-year-old boy, whose parents were away for the weekend, the night before.

The boy discovered the pair in his family's car parked in the garage of his home, in the affluent Pound Hill area of Crawley and raised the alarm.

Reports said the girls died from carbon monoxide poisoning after connecting a pipe to the car exhaust.

The car's engine was running when they were found and a length of hose was also discovered nearby.

One of the girls, whom police believe was 17, had travelled from the Republic of Ireland to stay with her 17-year-old close friend in the Broadfield area of Crawley for a short break.

Reports said they went to the boy's house on Saturday evening for a party with two other boys and decided to stay there when it became too late to go home.

Police believe the girls crept downstairs at some point during the night and took their own lives but do not know why.

The party host and his two friends, who were said to be "shocked and distressed", have been helping officers investigating the deaths piece together the events of the night.

A Sussex Police spokesman said: "This looks like a suicide pact, but we are trying to find out what pushed them into it."

He added: "Specially trained officers are comforting the family and friends of those involved in this tragic incident.

"Although our inquiries are continuing, we are not looking for anyone else in connection with the deaths."