OSLO Dec 28 (Reuters) - Output at the Statfjord A platform in the North Sea was shut down after an oil and gas leak on Saturday, leading to about half of the 168 staff on board being evacuated by helicopter, operator Statoil said.
The leak was reported at about 17.40 (1640 GMT) on board the platform. It was unclear what caused it.
The Statfjord field, one of the largest in the North Sea, lies some 180 km (110 miles) from the Norwegian coast and straddles British-Norwegian waters.
"Production was shut down," Statoil spokesman Kjetil Visnes told Reuters. "About half of the staff were moved by two helicopters to (platforms) Statfjord B and C."
There were no reports of injuries, he said, and the situation was being normalised from about 1820 GMT.
It was unclear when output would resume. Visnes declined to say how much oil and gas the platform was producing at the time of the incident.
Visnes said only production at Statfjord A was shut. He said he had no reports of Statfjord B and C being affected.
The Statfjord field produced some 129,000 barrels per day in December, or four million barrels for the month, and was expected to produce the same amount in January, according to loading schedules compiled by Reuters.
The field is expected to produce some 1.05 billion standard cubic metres of gas in 2013, according to estimates by the Norwegian Petroleum Directorate.
Statoil operates Statfjord and has a stake of 44.34 percent. The other partners are Centrica, with 34.29 percent, and ExxonMobil with 21.37 percent.