Nine people remained hospitalized Monday, including four Canadians, three Mexican employees of the hotel and two Americans. All were in stable condition, said Francisco Alor, attorney general of Quintana Roo state.
The resort, located south of Cancun, was hosting a large number of Canadians, including those attending a wedding and a company vacation.
The force of the explosion under the building blew out windows and ceiling panels and hurled paving stones and chunks of metal 50 yards away.
The blast happened in one of a dozen or so buildings that make up the hotel, and left a crater a yard deep.
Investigators believe the blast may have been set off by an accumulation of gases produced by decomposing material in the ground.
Officials said that investigators will try to determine if the hotel building, which sat on a concrete pad on a swampy area near the beach, had been properly constructed.
"Expert examiners and civil defense personnel will have to determine if the underground space filled with swampy water that remained in this zone when the building was constructed four years ago, could have generated this type of gases," Alor said.
Officials said no gas lines were located in the area where the blast happened.
The Associated Press Contributed to this report.