The gas first was identified as methane by officials but later was determined to be hydrogen sulfide. The Associated Press reported that crew members were replacing pipe connected to the Monarch of the Seas' sewage system. The broken line expelled an unknown amount of gas, and about 5 gallons of raw sewage into the starboard propeller shaft tunnel.

A supervising hazardous-materials specialist for the L.A. County Fire Department told the AP that the three crew members probably died within 30 seconds of encountering the gas.

The L.A. Coroner identified the victims as 47-year-old Boris Dimitrov, of Bulgaria; 41-year-old Willie Tirol, of The Philippines; and 48-year-old Radomilja Frane, of Croatia.