A man has been arrested in San Diego in the murder of his wife during a cruise to Mexico.

The FBI says Robert McGill of Los Angeles is being held in the death of his wife Shirley aboard the Carnival Elation.

Carnival says the 55-year-old woman was killed during a domestic dispute on Tuesday evening as the ship was midway through a five-night trip to Cabo San Lucas.

FBI and Carnival would not say how she was killed.

Crew members found the body and later detained McGill in the brig. The ship docked at its San Diego home port Thursday morning and the woman's body was removed.

The FBI sent about 20 agents to the ship in a U.S. Coast Guard Cutter Wednesday night while the ship was at sea, and they spent the night interviewing the suspect and 30 to 40 potential witnesses, Slotter said.

Passengers said they never got official word of what was going on, but rumors flew when they saw a security guard sitting outside the couple's cabin around the clock.

Passengers say they never got official word but rumors flew after a security guard was posted outside the couple's cabin.

"I get up and go to the gym at 6 a.m. and he would be there," said passenger Arlene Albi of San Diego. "I'd look down the hall when I'd go back down, during the day, and he would still be sitting there. I don't know if it was the same guy, but there was always someone in front of that room."

The ship docked at 6:30 a.m. Thursday, and the San Diego County medical examiner removed the woman's body about three hours later, said John Gilmore, a spokesman for the Port of San Diego.

The 2,052-passenger Elation left San Diego Saturday.

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