IGUALA, Mexico: Protesters occupied three town halls in southern Mexico on Thursday to demand the safe return of 43 students who disappeared after gang-linked police attacked them last month.

Students and teachers had threatened to enter all 81 municipalities in Guerrero state in the latest protest over a case that has caused national and international outrage.

But they only managed to seize the municipal buildings of three towns so far, the government said.

“We don’t have the capacity to seize all 81 municipalities in one day, so the plan is to do it progressively,” said CETEG teachers union spokesman Jose Angel Baron.

In the town of Huamuxtitlan, population 15,000, Mayor Johnny Saucedo told AFP by telephone that some 200 teachers had entered his building.

“We are respectful of the protest,” Saucedo said.

Protesters have also held the municipal headquarters of Chilpancingo, Guerrero’s capital, since Monday.

Guerrero’s CETEG teachers union and students plan to march in the resort city of Acapulco on Friday.

In Iguala, the town where the 43 students were last seen on September 26, municipal workers removed photocopiers and confidential documents as they evacuated city hall in anticipation of the protesters.

The city’s mayor, Jose Luis Abarca, and his wife skipped town after the students disappeared and they are now wanted for questioning over the incident.

Authorities say Iguala’s police force shot at buses carrying the students and handed them over to officers in the neighbouring town of Cocula, who then delivered them to the Guerreros Unidos drug gang.

Six people died, 25 were wounded and 43 students went missing that night. Authorities have since arrested 26 police officers from Iguala and 14 from Cocula.

The students, who are from a teacher training college in central Guerrero known for radical protests, had seized the buses to return home after holding a fundraiser in Iguala.

The discovery of mass graves around Iguala has raised concerns about their fate. DNA tests showed they were not among 28 bodies found in one location, but remains from other pits are being analysed.

The Iguala mayor’s sister, Roselia Abarca, told AFP that her brother was innocent and was eating tacos after his wife gave a speech when he heard about the police attack.

She said the day after the students disappeared, her brother told his family: “I leave my house and my children in your care. This will be fixed. Trust me.”

His family gathers every night to “pray for the students to appear and for him to be cleared,” she said.

Guerrero Governor Angel Aguirre said he had fired his administration’s health secretary, Lazaro Mazon, because he faces an investigation into his ties to Mayor Jose Luis Abarca.

Aguirre has himself rejected calls to resign. The case has embarrassed his leftist Democratic Revolution Party, of which the fugitive mayor is a member.

Tens of thousands of people marched for the students across Mexico last week while violent protests erupted this week in Guerrero, where demonstrators torched the state government headquarters.

President Enrique Pena Nieto, meanwhile, held another meeting with his security cabinet, saying he wanted to “accelerate” the investigation to find the students.

His government stepped up the search, deploying 1,200 federal police to look for the students in several towns,

Horse-mounted officers combed rough terrain, divers searched underwater and an aircraft overflew the area, the national security commission said.