Rohrer wrote that the product's distributor has said the degreaser contains no hazardous materials, is biodegradable and is harmless to the treatment process.
Pinetech E is made from the bark of pine trees and is used to break up grease and/or prepare for flushing operations, according to Rohrer's letter. Much of the material and grease is removed and captured downstream.
"This product is still being applied to Washington County collection systems not feeding the City of Hagerstown ... at similar dosage levels with no known ill effects," Rohrer wrote.
Greg Murray, the county's director of waste and sewer operations, said he's certain the county didn't cause the partial shutdown.
"There's no question at all," he said.
Murray said Pinetech E's distributor told the county it would take a tractor-trailer load of the product to cause problems at the plant.
"They said we didn't have the physical capacity to cause it," he said.
Murray said the state had also asked other waste-water treatment plants throughout the state about their treatment procedures, prompting the county to prepare a report about its sewer line maintenance procedures.
Murray said the toxic chemical might have come from anywhere in the city or the county, including dumping by trucks, industries or somebody pouring something down a manhole.
He said there's not enough information yet to determine who or what might have caused the problems.
"I wish there was," he said. "That would make things a lot less complicated."