What's bubbling up in the Squamscott River?

Officials in Exeter have a mystery on their hands. It's thick and it stinks.
They're trying to find out what's behind a mysterious tar-like substance that's bubbling up through the river and can be seen clearly on the river's bed during low tide. It covers a 20-foot by 30-foot area near the Swasey Parkway pavilion.

Don Clement, chairman of the conservation commission and the Exeter River Local Advisory Committee, and Ken Berkenbush, the town’s health officer and assistant fire chief, made the discovery while investigating complaints in recent weeks about a possible oil slick on the river.

Berkenbush and Clement walked along the river and searched by boat at high tide, hoping to find the source. Today they decided to investigate the substance at low tide. That’s when they saw it literally bubbling up through the topsoil.

Samples of the substance are now being tested at a state lab. Hopefully the results will come in soon and they'll get to the bottom of this potentially toxic situation. Until then, a boom was placed around the area to trap the substance and filter it out... good thing since the river is used for recreational boating, fishing and clamming and is also home to ducks and birds prey such as eagles, osprey, and hawks, which feed off the fish.