Blast hurts cleanup volunteers on Charles

Three members of a Charles River volunteer cleanup crew were injured yesterday when a taffy-like material they had pulled into their boat ignited, causing a small explosion. Two paramedics who responded to the scene suffered minor burns when they came into contact with the substance, authorities said.

State Police chemists were testing the substance, but officials said they do not believe it was placed along the shore of the Charles River with the intention of causing an explosion. Two of the boaters suffered first- and second-degree burns, but none of the injuries were life-threatening, said Jake Wark, spokesman for Suffolk District Attorney Daniel F. Conley.

The trash exploded near the Massachusetts Avenue bridge just before 2 p.m. The boat remained docked yesterday afternoon at the Gloucester Street landing as state investigators swarmed the site.

The crew members were volunteers for the Charles River Cleanup Boat, a nonprofit group that has been credited with clearing the river of trash and debris. Tom McNichol, the organization's president, said it is the first time anyone has been injured while combing through the assortment of debris found floating in the river.

McNichol speculated the substance may have been residue from the city's massive Fourth of July fireworks display, which is launched from the Charles River.

"Whatever it was, it looked harmless," said McNichol, who spoke to some of the volunteers. "The kid who picked it up said it looked like Styrofoam. He certainly didn't see it as being anything dangerous."

One of the volunteers, who said it was his first time on the cleanup boat, said the volunteers were in shock after the explosion. The volunteer, who showed investigators the rock wall where the crew came upon the substance, declined to give his name to a reporter.

"We were picking up trash, and the trash exploded," he said.

The material and the trash it touched apparently ignited after becoming wet, Wark said. "The position and placement of the substance do not indicate intentional placement, and its composition argues against its being any type of improvised explosive," he said.

The boat did not appear to have suffered structural damage. McNichol said he intended to take the boat out for its next cleanup mission, tomorrow.

He said he hoped the "bizarre" incident does not deter volunteers from participating. "We're totally dependent on volunteers making this system work," he said. Volunteers are instructed to avoid anything that appears potentially hazardous, he added. "Safety is the number one concern."

John C. Drake can be reached at jdrake@globe.com.