Public outrage over the disappearance of 43 students in Iguala, Mexico nearly two weeks ago swelled on Wednesday as thousands of protestors jammed cities across the country to demand that the government of President Enrique Peña Nieto solve the case of the missing youths — who are widely believed to have been massacred by drug gangs with ties to local police — and force those responsible to face justice.

An estimated 15,000 protesters marched through Mexico City’s streets carrying photos of the missing students and chanting slogans including “They were taken alive, we want them back alive,” and “I think, therefore I’m disappeared.” In Guerrero state, site of the disappearances, an estimated 50,000 demonstrators took to the streets, according to Mexican media outlets. In the state’s capital, Chilpancingo, an estimated 7,000 protesters blocked a highway that leads to the beach resort of Acapulco.

“Mexico has become worse than a death camp,” said Mariela López, a 56-year-old teacher who participated in the Mexico City march.

Protesters demanded that Guerrero state’s Gov. Ángel Aguirre Rivero resign and that Peña Nieto’s government find the missing students and punish local politicians linked to organized crime in Guerrero.

“I think these types of atrocities happen because the people in power think that they will always be on top, and nobody will be able to touch them,” said Marco, a 23-year-old university student who declined to provide his last name.

The 43 students, from a teachers college in the town of Ayotzinapa that caters to the poor and indigenous, went missing after they clashed with police in Iguala on Sept. 26. They had descended on the town to solicit donations and protest proposed government education reforms.

Guerrero Attorney General Iñaky Blanco said over the weekend that 28 bodies had been found at a mass grave outside Iguala, and that some of the missing 43 students were probably among the remains. Protesters on Wednesday demanded that an Argentinian forensic team be given complete independence to determine the identities of the bodies.

Blanco said local police officials had handed over 17 students to the drug gang Guerreros Unidos, a remnant of the Beltran Leyva Organization, a criminal group that was once powerful in the region and was recently decimated by the high-profile arrests of its leaders.

Nearly two dozen local police have been arrested in connection with the disappearances. The town's mayor, José Luis Abarca, is a fugitive. He is being investigated for links to the crimes, as is the head of security for Iguala.

The students’ disappearance is seen as part of the sustained violence in Mexico — an increasing problem for Peña Nieto, who has sought to shift attention from Mexico's gang violence to the economic reforms he has pushed through Congress. Peña Nieto took office two years ago, pledging to end a wave of violence that has killed about 100,000 people since the start of 2007. Homicides have fallen on his watch but other crimes, including extortion and kidnapping, have increased.