The National Transportation Safety Board has ruled that a helicopter crash in Maryland, USA, that killed four people including a British man last summer was accidental.
The report released this week says visibility was difficult because it was night time and there was fog in the mountainous terrain near the top of South Mountain late on July 23, 2009. Investigators did not find any mechanical malfunctions in the engine from before the crash.
The report states that the helicopter clipped and broke an unmarked, steel wire about 70 feet (20 metres) above Interstate 70 near Boonsboro. Witnesses said the helicopter struck a power line and burst into flames.
The crash killed 43-year-old Niall Booth, of New Market. Booth was originally from Dorking, England.
Also killed were the 24-year-old pilot and two other passengers.