British and American authorities were still trying to determine this week how more than 50,000 gallons of firefighting foam was released into a waterway near RAF Fairford on July 5.

Officials with the British Ministry of Defence, which operates bases such as Fairford that are used by U.S. Air Force units, did not respond to requests for comment on the matter this week.

Tech. Sgt. Keith Houin, a spokesman for the U.S. Air Force’s 501st Combat Support Wing that oversees Fairford, said Thursday that the cause of the discharge is still under investigation.

How the foam made its way to Dudgrove Brook in the nearby town of Fairford and on to the River Thames is also being investigated, Houin said Thursday in an e-mail.

About 700 fish were killed along a three-kilometer stretch of Dudgrove Brook as a result of the foam discharge, according to Dave Ferguson, a spokesman with England’s Environment Agency.

The EA is conducting its own investigation, but Ferguson said Thursday the incident has been “essentially closed down” by the EA because the foam is largely dissolved.

The foam made its way to larger rivers last weekend. Ferguson said it is not believed that the foam was hazardous to humans. An initial release on the spill sent out July 6 warned people that the foam could cause eye or throat irritation.

The brook is expected to recover on its own, and no water life has been reported harmed in the larger rivers into which the brook flowed, he said.

“It was diluted enough when it hit the Thames,” he said.

Water pollution and any fines or criminal penalties for such an act fall under the United Kingdom’s Water Resources Act, Ferguson said, adding that it’s difficult to say if any charges will come from the incident or what they may be.

Any future measures to prevent something like this from happening again will be addressed in the investigation, Houin said.

John Morgan, the mayor of the 4,000-strong Fairford, said it was “obviously a disappointment” that the spill happened, but he felt reassured by the EA regarding the scope of the issue and the protocols the Air Force has in place for such contingencies.

“We know they have the procedures,” he said. “We hope they don’t have to use them.”

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