An estimated 630 gallons of oil have spilled in a pipeline corridor on the Kenai National Wildlife Refuge in south-central Alaska.
The Department of Environmental Conservation says a survey crew discovered the spill in the Swanson River Oil Field Tuesday. Chevron notified authorities and shut down its active crude line in the area.
The cause of the spill hasn't been determined, though agency spill responder Steve Russell says the leak has apparently stopped.
Complicating matters, he says, is a huge swath of chest-high grass that must be cut for investigators to get a better sense for what happened and what the impact has been.