On Monday, protesters marched in several cities in Mexico to observe the second anniversary of President Enrique Pena Nieto's administration and to demand that the government find the 43 students from the Raúl Isidro Burgos Rural Teachers' College of Ayotzinapa who in Iguala, Guerrero, who went missing at the hands of police and are assumed to have been murdered.

In Chilpancingo, the capital of the southern state of Guerrero, demonstrators set their focus on attacking the state prosecutor's office, burning several vehicles outside and damaging windows and office equipment, The Associated Press reports.

An official of Mexico's Pemex oil company claims that protesters led by a teachers' union blockaded roads leading to a state-owned oil refinery in the southern state of Oaxaca, which interrupted automobiles from entering or exiting the area.

The official, who AP reports was not authorized to be quoted by name, said that the demonstrators did not go into township Santa Maria El Tule's oil refinery, so it did not need to close.

Spearheaded by a small group of parents of the 43 missing students, thousands of protesters marched along a main avenue in Mexico City.

The missing students were detained in the city of Iguala by local police in September. Prosecutors say they were handed over to members of a drug gang who reportedly killed them and incinerated their remains.

Since the Sept. 26 disappearance of the 43 students, there have been constant, mostly peaceful protests. The entire county has been galvanized by the events. Recently, after Amnesty International got involved, 11 people who were held in connection to the demonstration were released from jail.

Two new polls published Monday showed Pena Nieto's approval ratings falling to around 40 percent, which is some of the lowest levels of approval for a Mexican president since the economic crisis of 1994-1995.