Three people have been arrested in connection with the killings over the weekend of 10 Indians in the southern Mexican state of Oaxaca, officials said.

Denis Gutierrez, Wilfrido Solis and Sergio Hernandez are being questioned by prosecutors in Tuxtepec, a city about 100 kilometers (62 miles) from the scene of the massacre, Oaxaca Attorney General Manuel de Jesus Lopez said.

Gunmen opened fire Saturday on Indians traveling in several SUVs from the community of La Tani to the city of Santiago Choapam, where they planned to work in the upcoming municipal election.

Nine people were pronounced dead at the scene and a tenth died while being transported to a hospital in Tuxtepec.

Eight other Indians were wounded in the attack and three of them remain hospitalized, the Health Secretariat said.

Santiago Choapam is about 400 kilometers (248 miles) northeast of Oaxaca city, the state capital, and on the border with Veracruz state.

Investigators are looking at the possibility that the massacre was politically motivated because several groups have been vying for control of Santiago Choapam.

Two groups, one led by the family of former state legislator Damaso Nicolas, a member of the Institutional Revolutionary Party, or PRI, and the other by leftist Workers Party, or PT, member Cesar Mateos, have been fighting for control of the mountain city.

Nicolas is a "chieftain because his family has always had power, and now that other actors want to participate, they are against it and we blame them for the violence," Mateos said over the weekend.

The victims were buried Monday afternoon amid calls from their relatives for justice in the case.

Oaxaca is not only one of Mexico's poorest states, but it is also the state with the largest Indian population in terms both of absolute numbers and as a proportion of the total inhabitants.