UPDATE:  The test is complete. Special Operations personnel say the ugly sheen is just a form of algae and no hazard.

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CHATTANOOGA (WDEF) – The Chattanooga Fire Department is investigating a murky sheen on the Tennessee River.

The came in as a spill near the Aquarium on the Riverfront.

But it was not an obvious spill of some sort.

Fire crews have put out river booms as a precaution to keep it from spreading.

They have gathered samples to have the water tested.