Three crew members were killed and 20 others injured after sewage gushed from a pipe being repaired inside a crowded Royal Caribbean cruise ship docked at the Port of Los Angeles, releasing deadly levels of hydrogen sulfide gas.
Crew members aboard the Monarch of the Seas were trying to fix the pipe in a roughly 10- by 12-foot portion of a propeller shaft tunnel on the starboard side of the ship about 9 a.m. when the accident occurred, officials said.
The workers thought the pipe would be empty, but when they opened it, gas-laden sludge burst out of a 5-gallon sewage container, firefighters said.
Their deaths were "almost instantaneous," said Barbara Yu of the Los Angeles County Fire Department. "Hydrogen sulfide is a deadly gas, and it's heavier than air."
The amount of gas the crewmen inhaled was believed to have been four times the lethal level, Yu added.
Hydrogen sulfide is a sewage byproduct generated by decaying organic material. Also known as sewer gas, it smells like rotten eggs.
At low levels, it can irritate the eyes and throat, but at high concentrations, even a few breaths can cause sudden death.
Officials do not know what triggered the malfunction. The three workers were not wearing protective gear or breathing equipment during the repair effort.
U.S. Coast Guard inspectors had checked the ship's sewage system as part of a routine examination in March and found no problem, a Coast Guard spokesman said.
The Monarch of the Seas had just docked at the port after a four-day voyage to Ensenada and had 2,649 passengers on board when the rupture occurred.
They were all evacuated, and none were hurt.
Among the injured were two ship physicians and a nurse who responded immediately after the accident but were felled while they were administering CPR to their shipmates, said Melissa Kelley, a spokeswoman for the Los Angeles Fire Department. None were seriously hurt, said Fire Battalion Chief Lou Roupoli.
The injured were aided by the ship's on-board fire team, whose members wore breathing apparatus and pulled some of the crew to safety, officials said.
A spokesman for Royal Caribbean Cruises declined to name the dead.
Dennis Lindoff, a passenger from British Columbia, said he was sitting with his wife on the fourth deck with his luggage when he heard an announcement on the public address system asking certain crew members to go to the starboard engine side.
"I really thought, 'Maybe this is a drill,' but it turns out it is not," said Lindoff, who has taken the same cruise several times. "I'm very upset about it. The crew members -- you get to know them, and they're really great people. You really get to know a few of them quite well."
Shawn Dailey and Angela Hodge, friends who took the cruise together, said the stench was inescapable.
"We didn't know anything," said Dailey, 35, of Mission Viejo. "We had no idea what was going on. But it smelled like a sewer."
Hodge, a 32-year-old Long Beach resident, said, "I just smelled a bunch of funky stuff.... I seen them taking some people in an ambulance. I've seen them give people oxygen. And I was like, 'What's going on?' "
Coast Guard spokesman Tony Migliorini said it was normal for a ship's crew to carry out maintenance while in the port but that clearly sewage should not have been in the pipe when it was being replaced.
"Of course, clearing the lines before they made repairs would have been the No. 1 thing to do," he said. "And, of course, if they knew there was something in the line, having some kind of breathing apparatus.
"Hopefully, from the lessons learned in this case, the next time somebody goes to repair a sewer line, they'll ensure there are some safety precautions taken," Migliorini said. "The fact that there was sewage in the line was obviously the problem, but we don't know why it was there."
Coast Guard Lt. Cmdr. Dennis Miller, chief of the inspection division in Los Angeles, said ship sanitation systems are examined as part of the Coast Guard's regular vessel inspections, conducted at least every six months.
Although he would not disclose the results of the ship's March checkup, he said there were no outstanding problems with the sewage system.
"We do know the vessel doesn't have any deficiencies with their sewage system prior to today," he said.
Inspectors look for leaks, either of liquids or methane and hydrogen sulfide.
Ships such as the Monarch, which have enough passengers to fill a small village, have their own simple sewage treatment systems, typically consisting of several marine sanitation devices in the hold.
Wastewater is piped to tanks, where it is exposed to air and bacteria, which break down the pollutants. It is then disinfected with chlorine before discharge, which California bars within three miles of shore.
The Monarch of the Seas is a 74,000-ton luxury liner that journeys along the Baja coast. It can carry up to 2,744 passengers and made its maiden voyage in 1991 for Royal Caribbean, the nation's second-largest cruise line behind Carnival Cruise Lines.
The accident Friday was believed to be the first deadly mishap on a cruise ship since a 2003 explosion on the Norway in the Port of Miami killed eight seafarers and injured 17 others.
In 1986, a methane and sulfide gas leak from a sewage tank killed four crew members in Jacksonville, Fla., aboard the Scandinavian Sky.
Michael Crye, president of the International Council of Cruise Lines, said cruise ships were still one of the safest modes of transportation, adding that no passengers had been killed on a cruise line in recent memory.
"It's a very, very safe vacationing experience," Crye said. "We're shocked and very much saddened by this. We hope that everyone concerned with the industry takes this issue very seriously."
The industry has drawn criticism in recent years for hiring seamen from poorer countries, having them work long hours and live in cramped quarters, and paying them wages well below American standards.
Royal Caribbean spokesman Michael Sheehan declined to say Friday what nationality the dead crew members were.
Local authorities said the ship's officers were Norwegian.
The injured were taken to several area hospitals. Four were treated at Little Company of Mary San Pedro Hospital and released.
One injured crew member, still dressed in his hospital gown, declined to discuss the incident as he walked out of that hospital Friday afternoon.
Another patient was treated at Harbor-UCLA Medical Center near Torrance. A spokeswoman declined to disclose that patient's condition.
"Our thoughts, prayers and heartfelt sympathies go out to the victims of this accident," said Capt. William Wright, senior vice president of marine operations for Royal Caribbean International, in a statement.
Times staff writers Bettina Boxall and Stuart Pfeifer contributed to this report.