Gas Leak Shuts Down L.A. Harbor : Shipping: The port reopened late Friday night after threat eased. A flammable chemical had leaked aboard a freighter, raising fears of an explosion.

The Port of Los Angeles was closed to major cargo and passenger ships virtually all day Friday after authorities discovered a highly flammable chemical leaking aboard a freighter docked on the western side of Terminal Island.

The harbor was reopened minutes before midnight but not before causing major disruptions in port traffic.

The leaking cargo--which officials eventually learned included a second, less-flammable chemical--prompted the Coast Guard to shut down the main channel of the harbor to all shipping traffic.

Authorities initially said the incident posed the threat of a major explosion, and officials from a variety of agencies--including the Los Angeles Fire Department, Coast Guard and the South Coast Air Quality Management District--prepared for an evacuation of substantial portions of Terminal Island and San Pedro, fearing that moving the cargo might cause it to ignite.

Late Friday, however, authorities determined that the leaking gas was not nearly as concentrated as they initially thought, which made the situation far less dangerous.

After authorities reassessed the danger, risk management teams began unloading the cargo containers carrying the hazardous chemicals from the container ship Ever Group The harbor was officially declared open at 11:41 p.m., according to Battalion Chief Wes Hawkes of the Los Angeles Fire Department, and harbor officials expressed confidence that business would be back to normal today.

Authorities spent Friday trying to figure out how to deal with the leak. They at first believed that substantial concentrations of trifluoropropene, a highly flammable gas used in the manufacture of plastics, had escaped from a pressurized canister into a cargo container stowed in one of the vessel’s holds. They feared that removing the gas would cause an explosion.

But by late Friday, follow-up testing showed that the concentrations were low enough to allow for safe removal of the leaking cargo.

It was unclear whether the concentrations had dissipated over the course of the day, or whether they were simply less than officials originally suspected.

“Knowing what I know now, we would have all been at home by now and I wouldn’t have set half of these safety procedures,” Deputy Chief Donald F. Anthony of the Los Angeles Fire Department said late Friday.

The tests also turned up a second leaking chemical--trimethyl phosphite--which was stored in 55-gallon drums in two other cargo containers aboard the ship. That chemical, although far less flammable than the trifluoropropene, is believed to have caused the foul odor that initially drew attention to the ship earlier in the week.

Friday’s shutdown was the first time the port had been closed by an incident involving hazardous cargo since the disastrous explosion of the oil tanker Sansinena in 1976. Nine men were killed in that blast, which caused $21.6 million in damage.

Port officials had their first inkling that something was amiss aboard the Ever Group Wednesday afternoon, when a strong odor forced longshoremen to stop work aboard the Taiwan-registered 890-foot container ship, which is operated by the Evergreen International shipping company.

According to port spokeswoman Julia Nagano, at least two port police officers and two longshoremen who were on the scene when the vapors were first detected became ill after breathing them. They were treated at a hospital and released, she said.

Because of shifting winds, authorities were not able to trace the smell to the Ever Group until Thursday, when air samples detected the presence of trifluoropropene

Chief Anthony said the gas had arrived here by rail from the Midwest and was loaded onto the Ever Group for shipment to the Far East.

The discovery caused widespread concern in the harbor.

On Thursday night, 27 “non-essential personnel”--most of them relatives of staffers--were evacuated from the federal penitentiary at Terminal Island about half a mile south of the ship. They were housed in a Long Beach hotel. Officials said arrangements had been made to house the 1,127 inmates at other prisons and jails if further evacuation proved necessary.

Half of the approximately 100-member Coast Guard contingent at Reservation Point--the southernmost point on Terminal Island--were evacuated and several commercial fishing vessels and sportfishing boats berthed along the main channel were ordered to remain at their docks.

The passenger ships Azure Seas and Southward were diverted to berths in Long Beach Harbor and four cargo ships were stalled at anchor in the outer harbor. Other freighters, scheduled to sail on Friday, were marooned at their docks. Officials said such delays typically cost about $40,000 a day per ship.

The decision to seal off the main channel between Reservation Point and the Vincent Thomas Bridge--a distance of about two miles--was made at about 10 p.m. Thursday to create a safety zone around the Ever Group.

The main channel is the only route that big passenger and cargo ships can use to reach the berths at the Port of Los Angeles.

There is a smaller, secondary route--the Cerritos Channel--that some smaller vessels can use to enter the port through the adjacent Long Beach Harbor. However, for much of Friday, the Commodore Schuyler F. Heim Drawbridge on the Terminal Island Freeway was stuck in the closed position, sealing off the Cerritos Channel.

Times staff writers David Ferrell, Sheryl Stolberg and Jocelyn Stewart contributed to this story.