Mexico City is bracing for demonstrations as caravans of students and family members of 43 missing college students converge on the capital after several days crisscrossing the country.

Three marches demanding justice for the students from a rural teachers college, who disappeared on Sept. 26, are to merge Thursday evening in the city's central square.

The government has said gangsters in the southern state of Guerrero killed and incinerated the students after police in the town of Iguala intercepted them on the mayor's orders and turned them over to the criminal group Guerreros Unidos. Their families have rejected that account and the marches aim to keep the pressure on the government to find them.

Demonstrators temporarily blocked a road to the airport Thursday, but it has continued to function normally.