Investigators traced an oil spill that was leaking into the Charles River to a drainage pipe in Waltham, Massachusetts.
The leak was first reported around 5 p.m. Wednesday on River Street, near Shaw's Supermarket. Containment booms were placed to prevent the spill from expanding.
Officials traced the drainage system into piping and manholes, where they saw some oil in the piping, according to the Massachusetts Department of Environmental Protection. Environmental contractors vacuumed an estimated 300 gallons of water and oil mixed together, authorities said.
Samples were taken to determine if the oil in the pipes and the river are the same.
Heavy machinery was used Wednesday night to begin the clean-up process and crews began to open manholes in an effort to detect the spill's source. Absorbent materials were placed Thursday to clear the river's surface from oil.
The cause of the leak and the source for the oil remains under investigation.
