A total of 176 people were arrested when police stormed three schools in the western Mexican state of Michoacan, where students were holding 82 commandeered vehicles belonging to foreign businesses, state officials said.

The police operation, launched in the pre-dawn hours on Monday, was aimed at recovering the more than 50 buses and delivery trucks seized on Oct. 4 and taken to three normal schools in an area of Michoacan populated by Purepecha Indians.

The schools are located in the cities of Cheran and Arteaga, and the town of Tiripetio.

Students set 13 vehicles, including buses, patrol cars and private vehicles, on fire.

The students had seized vehicles belonging to Coca-Cola and Sabritas to protest changes to the curriculum at Mexico's normal schools. Those institutions - once common in both Europe and the Americas - prepare young people for careers in teaching.

Federal Police officers used tear gas, helicopters and armored vehicles to break up the protests.

Purepecha Indians clashed with police four times after officers entered Cheran, the only city in Mexico governed under traditional law.

Students from the normal school in Tiripetio confronted police, but many of them ended up fleeing into nearby fields and a Catholic church.

Students and teachers belonging to the CNTE, the union that represents most of Michoacan's teachers, seized two tractor-trailers late in the afternoon and used them to block the road that links Morelia, the state capital, to Tiripetio.

State police used riot equipment to break up the roadblock and arrested seven teachers, including CNTE Local 18 secretary-general Juan Jose Ortega Madrigal, who was released Monday night.

Ortega Madrigal was charged with blocking a federal highway.

The CNTE paralyzed 80 percent of the elementary schools in Michoacan's 113 cities to protest the police operation.

The National Human Rights Commission, or CNDH, said Monday night that it would send a team of observers to Michoacan made up of lawyers, doctors and psychologists to determine whether residents' rights had been violated and to get a firsthand look at the treatment of prisoners.

President Felipe Calderon is expected to visit several towns in his native Michoacan, including Cheran, on Tuesday. EFE