A wave of violence linked to powerful drug cartels has sent the number of missing persons in the country soaring to more than 36,000, and families of the "disappeared" often search fruitlessly for them for months or years.
Guadalajara, the country's second-largest city, has been hit particularly hard by the violence as home base to the brutal Jalisco New Generation Cartel.
It emerged over the weekend that the city's morgues are so full, authorities decided to rent a refrigerated trailer to hold the bodies of 278 murder victims.
The truck caused outrage when the authorities parked it in a series of impoverished neighborhoods on the outskirts of the city. Residents protested over the smell, flies and risk to public health.
Officials then moved it to a prosecution storage facility in the city center. The governor has fired the state prosecutor and coroner over the debacle.
The gruesome affair drew some 100 people from across the country to the western city, where they demanded to know if their loved ones were among the bodies.
"When I heard this awful news, I said, we have to go," said Yadira Gonzalez, 36, who has been searching for her missing brother Juan for 12 years, and belongs to a group for people with missing relatives in the central city of Queretaro.
They drove some five hours to picket outside the Institute of Forensic Sciences for Jalisco state, of which Guadalajara is the capital, demanding to know whether their loved ones were in the truck.
"Our family members disappeared in Queretaro, but they could be anywhere in the country, really," said Gonzalez.
'We've lost all trust'
News media have broadcast footage of the open trailer of the truck, with piles of bodies in black bags and a man in white boots stepping on the bags.
"Society has lost all trust in government institutions and their leaders," said another woman seeking a missing family member, Guadalupe Aguilar.
"That's why we're here picketing. We won't leave until we get answers."
The number of murder victims in Mexico has exploded in recent years.
Since the government deployed the army to fight the country's powerful drug cartels in 2006, Mexico has been hit by a wave of violence that has resulted in more than 200,000 murders.
Last year, the country registered a record 28,702 homicides.
Mass graves are regularly discovered containing dozens or even hundreds of unidentified bodies. Nearly 4,000 such corpses have been found since 2007, according to the National Human Rights Commission.
Authorities in Guadalajara also began a three-day DNA testing clinic on Monday, where relatives of the missing can complete a genetic profile in hopes that coroners or investigators will one day find a match.
Juan Francisco Flores, who is searching for his missing son, had already been through the process several times.
Juan Jr. disappeared in March 2016, aged just 16.
"Unfortunately I've done all this before, to no avail. I've given DNA samples here, at the federal prosecutor's, in a lot of places, and nothing has come of it," Flores told AFP, his voice breaking.