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 peacefully occupied government buildings in the towns of Tlapa de Comonfort, Atoyac de Alvarez and Huamuxtitlan, after vowing to enter all 81 municipalities of Guerrero state, police said.
Protesters have held the municipal headquarters of Chilpancingo, Guerrero's capital, since Monday.
Huamuxtitlan Mayor Johnny Saucedo told AFP by telephone that some 200 teachers had entered his building.
"We are respectful of the protest," Saucedo said.
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 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 neighboring 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.
Authorities have exhumed several mass graves on the outskirts of Iguala, but officials say DNA tests so far show that the remains belong to victims of other crimes.
The case has sparked international condemnation and outrage at home, with tens of thousands of people demonstrating nationwide last week and violent protests erupting in Guerrero this week.
On Wednesday, protesters threw rocks at the windows of the attorney general's office in Mexico City.
Guerrero's CETEG teachers union and students plan to march to the resort city of Acapulco on Friday.
"We don't have the capacity to seize all 81 municipalities in one day, so the plan is to do it progressively," said CETEG spokesman Jose Angel Baron.
More troubling discoveries are being made around Iguala, where 80 bodies have been dug up since February.
Vigilantes who have been searching for the students said they found six more burial pits on Wednesday, though they contained just one bone and some shoes.
Mexican President Enrique Pena Nieto, meanwhile, held another meeting with his security cabinet, saying he wanted to "accelerate" the investigation to find the students.