Long before 43 teachers college students disappeared in an attack by police, Maria Guadalupe Orozco's son went missing in the same southern Mexico city of Iguala.

Orozco says Mexican soldiers took Francis Garcia Orozco as he was ferrying equipment between a nightclub and the fairgrounds for a festival, an assertion based on witnesses and grainy security camera footage that day in March 2010. The military denied it.

Now she wonders if he's among the 28 bodies found in five burial pits at a clandestine mass grave uncovered during the all-out search mounted by authorities for the missing students. Officials say none of college students was among the remains recovered, so rather than solve an extraordinary crime that has captured international attention, a mass forced disappearance by the state, the discovery of the bodies has added layers of horror to a situation already difficult to fathom.

Instead of finding the 43, authorities are asking "Who are the 28?" Guerrero has long been a stronghold for both leftist guerrillas and drug traffickers, so the dead could be both. Or neither.

Given Mexico's record on identifying the missing, Orozco may never know if her son is among them.

"It's like reliving those days of anxiety, desperation, of wishing and asking God for the telephone to ring," Orozco said of the grisly find. "If anyone knocks on the door at any minute, you think, 'He's here now.'"

The government of President Enrique Pena Nieto took office two years ago saying it would make a verifiable list of the missing in Mexico, and released a searchable database of 22,322 people in August. Government officials, who say at every turn that violence has dropped dramatically on their watch, put little attention on the fact that 9,790 of those people — more than 40 percent — have gone missing since Pena Nieto took office.

The rest were from the previous six years under former President Felipe Calderon, when disappearances began to spike with his attack on organized crime.

The list does not include the 43 students of the radical Rural Normal School of Ayotzinapa. The government says it still does not know what happened to the young people after they were rounded up by local police in Iguala and allegedly handed over to gunmen from a drug cartel Sept. 26, even though authorities have arrested 50 people allegedly involved. They include police officers and alleged members of the Guerreros Unidos cartel.

In an analysis of the database numbers by the newspaper Reforma, Guerrero is not even on of the top six states with the most disappeared. Tamaulipas, where 72 migrants were slaughtered in 2010 and hundreds more found in mass graves the following year, was No. 1. Jalisco, home to Guadalajara and warring drug cartels was No. 2. Some 67 people were found in mass graves there just last Christmas.

Mass graves are regularly found around the country — 11 bodies in August in Michoacan state, 19 others in Iguala just last May.

Figuring out who they are is the government's challenge, and progress is slow despite the creation of a special unit of the Attorney General's Office in May 2013 to find the missing. Mexico has had no national database to match characteristics of missing to unidentified dead, and is in the process of building one from scratch. Although the government finally has a list of the missing, there is no official number of unidentified bodies, according to the Attorney General's Office.

The Attorney General's Office won't release results of the team's work so far. But a Human Rights Watch statement earlier this month gave a scathing evaluation of the government's handling of the missing, saying the team has reviewed only 450 cases and located 86 people, of which 57 were alive and 29 dead.

The rights group also criticized the federal government for cutting its proposed 2015 allocation to the unit by more than 60 percent.

"What I always say is that nothing we could do is enough," said the federal assistant prosecutor for human rights, Eliana Garcia, adding that she expects the missing database to be accessible nationwide by 2016. "They're right to be angry; they're right to be frustrated. I'm frustrated."

Only six of 32 states so far have the International Red Cross software designed to match missing persons with unidentified bodies, a program that asks not only DNA and fingerprints but characteristic and habits of the person who disappeared.

In Mexico City, where there are more workers available to build a database, officials of the Institute for Forensic Science have 13,000 unidentified bodies going back to 1980, and it took a month to upload 20 of them into the database.

The institute only started collecting DNA samples on all unidentified corpses this year. The data searches are still done by hand.

"We get a thousand requests a year from all over the country asking us to look in our archives," said Maria Antonieta Castillo, head of identification services. "We've only given about three positive identifications."

Attorney General Jesus Murillo Karam announced the formation of his agency's identification unit three weeks after relatives of young people who had gone missing staged a hunger strike in May 2013.

Erika Montes de Oca, one of those protesters, said the case of her nephew was one of the first solved by the attorney general's team. Sergio Guillen Eduardo Montes de Oca, 27, disappeared from a bar where he worked in the center of Mexico City in November 2012.

"It says one thing: When you seek, you find. He had been in a mass grave for eight months," Montes de Oca said.

Now she works for the team helping other families.

"In one year, I've found two girls, one dead and one alive. For me that's success," she said. "We're trying."

But it doesn't seem so in Iguala, where Felix Pita's 17-year-old son, Lenin Vladimir, disappeared with Garcia more than four years ago, and where 43 more desperate families are now demanding to know what happened to their missing.

"We're going to keep protesting until there are positive results," said Pita. "If we don't, they will disappear all of us."


Associated Press writer Maria Verza reported this story in Mexico City and Christopher Sherman reported in Iguala.