Firefighters, police and private company refrigeration technicians worked for about four hours yesterday morning to stop an ammonia gas leak at a cold storage warehouse in Campbell Industrial Park.

The leak was reported about 4:30 a.m. at Hawaii Logistic Services at 91-315 Hanua St.

Police blocked off access to Campbell Industrial Park and evacuated some businesses affected by winds blowing from the direction of the leak.

"Basically, we just cordoned off the entire block (around the building)," said police Maj. Michael Moses. "And that was sufficient, based on the information we got from the fire department."

Fire Department spokesman Capt. Terry Seelig said firefighters assigned to a hazardous materials team worked with the private refrigeration company technicians to "manipulate some valves" in order to cut off the flow of ammonia to the leak.

But because ammonia remained in the line between the valve and the leak, some of it continued to escape, Seelig said.

Seelig said about 100 pounds of ammonia was released. HPD firefighters wore full-coverage hazardous materials suits to reach the area.

Firefighters entered the warehouse to find out how much of the leaking gas remained and how much of a problem it posed, Seelig said. By about 8:15 a.m., the hazard to the surrounding area had been averted, so the roadblock was lifted, allowing motorists to enter the park.

The ammonia leak area inside the building remained isolated and was monitored during the day until the fumes were safely ventilated, Seelig said.

The ammonia leak was the fourth incident in the industrial park area in less than three weeks. All four incidents happened on two roads, Hanua Street and Kaomi Loop.

Moses said a rash of incidents in such a short time was probably nothing more than an anomaly.

"The area has been relatively problem-free until this last month," he said. "And then we had the tower collapse, the fire, the chlorine leak and now this."

The series of events began on May 16, when a worker was crushed to death after a 120-foot cooling tower collapsed at the Hawaiian Cement facility on Kaomi Loop.

Then, in the early morning hours of May 22, about 30 firefighters battled a blaze at Schnitzer Steel Hawaii Corp. on Hanua Street.

Later that afternoon, on Kaomi Loop, dozens of fire and police officials evacuated the industrial park for four hours after a chlorine leak from a one-ton steel cylinder at B.E.I. Hawaii triggered health concerns about heavy winds spreading toxic fumes as far as Makakilo.

"Chlorine has a much higher level of toxicity than ammonia," said Seelig. "Ammonia is pretty toxic in itself."

There were no injuries in the Schnitzer fire, the chlorine leak evacuation or yesterday's ammonia leak incident.