The spill has been contained and the leak stopped after workers discovered a sheen on the water.
Twenty-four hours after discovering the leak, several layers of containment boom are now fencing in what some estimate to be up to a dozen barrels of crude oil.
"We've got good containment. We've isolated the source of the oil, we believe. We're doing more investigations within the plant, but we haven't seen any more oil discharged," said Scott Dean, BP spokesperson.
Officials say the spill appears to have originated at the plant's water cooling system, though it's unclear how the oil made its way in there to begin with.
"It appears to have been an isolated incident, but we're obviously going to go through the plant with a fine-tooth comb to make sure something like this never happens again," said Dean.
Eager to show the public what they say is the limited scope of the spill, BP allowed Eyewitness News cameras onto the beach where cleanup crews were using shovels and rakes to bag and dispose of whatever is washing up. Crews say the cold weather and northerly winds are pushing the oil to shore and facilitating the effort.
"It's hardening up, whatever that stuff is," said James Ward, cleanup crew.
Also helping to contain the spill is its geographic location within an artificial cove created by the refinery on one side and a steel mill on the other. Environmental Protection Agency officials on site Monday say they hope to limit any environmental impact on Lake Michigan.
"There's been no evidence of any sick wildlife, there's no evidence of anything that would affect the wildlife in that manner. BP is monitoring the air for any impact to human health for their own workers and the public around," said Mike Beslow, EPA.
Both the EPA and the U.S. Coast Guard have been overseeing the clean up efforts. They say that most of the affected shoreline, about 2,700 yards, has already been cleaned up, but a more comprehensive assessment is scheduled for Wednesday.