DUTCH HARBOR -- The Coast Guard says a hazardous materials team is venting a fishing vessel that's leaking toxic ammonia near Dutch Harbor.

Petty Officer Jonathan Klingenberg says the team also plans to conduct atmospheric tests on Tuesday to measure levels of ammonia still leaking from the Seattle-based Excellence, a catcher-processor.

The ammonia leak on the 353-foot vessel began Friday while it was docked at Dutch Harbor. The Excellence has since been towed six miles to Wide Bay.

The Coast Guard says the slow leak is believed to be coming from a tank holding up to 5,000 pounds of ammonia. The entire cooling system on the 353-foot Excellence contains 20,500 pounds.

State regulators say three people on board the vessel have been treated for inhalation of ammonia vapors.