According to Mexican authorities, the explosion occurred at the Kool Beach restaurant along the coast.
The restaurant is in a popular tourist zone of the Playa del Carmen resort, south of Cancun, and three of the injured people were apparently customers, though no information on their nationalities was immediately available. The other people injured in the blast were also restaurant employees, officials said.
Prosecutors in the coastal state of Quintana Roo said eight of those injured at the Kool Beach restaurant had been released from hospitals.
State police chief Lucio Hernández wrote in his social media accounts that the blast occurred "in a gas tank in the kitchen of the restaurant."
Photos from the scene appeared to show windows blown out and an awning collapsed.
It would not the first time that poor management of cooking gas lines has resulted in deadly accidents on Mexico's Caribbean coast.
In 2018, a gas leak in a water heater caused the deaths of an American couple and their two children in the resort town of Tulum, south of Playa del Carmen. An inspection revealed that the water heater at the rented condominium was leaking gas. Prosecutors said the gas leak was perhaps caused by a lack of maintenance or the age of the equipment.
In 2010, the explosion of an improperly installed gas line at a hotel in Playa del Carmen killed five Canadian tourists and two Mexicans.
In that case, prosecutors said the gas line, apparently meant to fuel a pool heating unit, was not properly installed or maintained. They said gas leaking from the line may have been ignited in an explosion by a spark from an electric switch or plug.
Mexio's Caribbean coast, the country's most popular tourism destination, has been battered by drug violence in recent years.
The Associated Press contributed to this report.