The cleanup of an oily spill in the Flint River continues a week after it was first detected, and officials said Tuesday they still don't know the source.
The oily substance was discovered leaking into the river through a storm drain outfall a short distance upstream from the University of Michigan-Flint campus.
So far, the city said, crews have recovered about 1,200 gallons of the oily-watery mix. The spill is contained, and booms remain in the river in parts of downtown Flint.
The city said this is the fourth mysterious oily spill in the river in the past 12 months.
Flint city officials speculate that soil contamination or illegal dumping could be the source of the spill.
Crews have been trying to trace the source through local sewer lines but have been unable to pinpoint its origin or composition.
