( CNN ) -- Frozen winter conditions are helping slow the spread of a pipeline leak on Alaska 's North Slope , an environmental official said . An estimated 46,000 gallons of a water-and-oil mixture was spilled before the source of the leak -- a pipe rupture -- was identified Monday , according to the Alaska Department of Environmental Conservation ( ADEC ) . The ruptured 18-inch line , owned by oil company BP and which usually carries a mixture of 75 percent water and 25 percent oil , has been repaired . The frozen conditions make the spill less mobile , Matthew Carr of the U.S. Environmental Protection Agency said late Wednesday . `` Any spill is regrettable , '' Steve Reinhart , a BP spokesman in Anchorage , told CNN . `` We will clean this up thoroughly and our investigation will find out what happened so that we can ensure this does n't happen again . '' Reinhart said the spill , which occurred entirely on land , has had no impact on production or wildlife in the area , and is contained to a small fraction of the much larger Prudhoe Bay oil field . `` It is not a pool of oil spreading out across the ground , '' Reinhart said , comparing its consistency to that of a snow cone . `` It 's a partially solidified mass that 's piled up in one area , and as we speak , truckloads of this material is being moved off this site and to a collection depot . '' According to officials , the rupture was approximately 24 inches lengthwise , running along the bottom of the pipeline . In an incident report on its Web site Wednesday , ADEC described the rupture as being `` consistent with an overpressure scenario , '' caused by ice inside the pipe . The leak was discovered early November 29 by a BP worker conducting a routine inspection . The North Slope 's biggest spill to date happened in 2006 when a corroded pipeline dumped 200,000 gallons of crude oil . CNN 's Nick Valencia contributed to this report .
Ice buildup led to Alaskan pipeline rupture , officials say . Nearly 46,000 gallons of water-and-oil mixture spilled entirely on land . Spill not believed to have any effect on production or wildlife in area .