“On Thursday night, about 20 people were abducted by armed men as they arrived in Acapulco. There is no immediate word on their whereabouts, the suspected kidnappers or their motive,” a police investigator says.
The tourists are from Morelia in the Michoacan state, which is the base for La Familia, a powerful drug carted in Mexico.
An armed group abducted the tourists on Thursday, and at least two of the abducted people have managed to escape, police says.
Northern Mexico is gripped by a wave of violence which has killed 34 in two days, authorities say.
In the town of San Jose de la Cruz, presumed rival drug gangs clashed in a bloodbath that left 14 dead, a local prosecutor says.
Two drug cartels, the Sinoloa and the Juarez cartel are clashing in the northern states over the control of illegal drug routes.
More than 28,000 people are believed to have been killed in drug-cartel related violence in Mexico since late 2006, when President Felipe Calderon launched a crackdown.