Part of the main road from Belfast to Derry was closed tonight as severe weather hit the north west of the province.
Motorists were urged to avoid the Glenshane Pass as traffic ground to a standstill in the blizzard conditions.
Police said they have closed one end of the pass at Maghera and are considering closing off the other end at Limavady.
Mary Nelis, the Sinn Fein Assembly member for Foyle, blamed the Department of the Environment Roads Service for failing to grit the road.
“How many times have we to point out to Roads Service that they should listen to the weather forecasts?” she asked.
“They should know that the Glenshane Pass, which is 1,000 feet above sea level, must be gritted. It is the main road to Belfast for hundreds of people.”
A spokeswoman for the roads service said the Met Office had predicted snow at midnight but it came sooner than expected.
“There are gritters on their way and hopefully the road will be open as soon as possible,” she added.