GLOUCESTER CITY, N.J., (CBS) — The Coast Guard is responding to a report of tar balls along the Delaware River.

The Coast Guard Sector Delaware Bay in Philadelphia received a report Friday from the National Response Center of oil (tar balls) along the shoreline of Gloucester City, N.J.

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The Coast Guard says initial reports of some tar balls have increased to more of a slick along the shoreline.

The amount and source of the oil is unknown at this time.

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The Oil Spill Liability Trust Fund has been opened and an Oil Spill Response Organization is conducting cleanup operations.

Samples have been taken and the Coast Guard is investigating the spill.

Stay with for the latest on this developing story.

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