Mexico now has a backlog of more than 30,000 unidentified corpses as murder rate soars

The country's murder rate has soared by more than 30 per cent, smashing national records for two years running, news.com.au reported.

In 2018, there were 33,341 murders, a 33 per cent increase over the record-breaking 2017 toll of 25,000 — at the time the highest rate since 1997 when the record began.

The crisis is so bad that authorities can no longer cope with the volume of victims. There are now an estimated 30,000 unidentified corpses languishing in morgues and refrigerated trucks across the country.

In one particularly horrifying case, a "wandering" refrigerated truck carrying corpses from an overflowing morgue in Guadalajara was forced to park on the outskirts of the city following complaints about the smell.

The truck was initially thought to have been carrying 157 bodies but after authorities provided a warehouse in which to store them, they found far more — at least 273 — crammed inside.

In a 2018 report headlined "Stinky trailer angers residents" the Mexico News Daily said locals were so disgusted by the smell — some even claimed to have seen blood leaking from the container — they threatened to set it on fire.

The trucks — known as "morgues-on-wheels" — have become an increasingly familiar sight as drug cartels amp up their murderous campaigns, generating more victims than authorities can cope with.

A report released by Mexico's National Human Rights Commission last week said there were now more than 30,000 unclaimed and unidentified corpses and an uncalculated number of skeletal remains piling up at morgues and makeshift morgues.

The agency said there was "a crisis in the area of forensic identification" because morgues lacked funds, staff and equipment to properly examine bodies.

Some, such as the morgue in Guadalajara, were so overcrowded and poorly run bodies were left to rot for up to two years before being autopsied, according to AP.

But it's not just drug cartels doing the killing — the country's security forces are believed to have played a role in more than 37,000 "enforced disappearances".

"Since 2006, enforced disappearances by security forces have been a widespread problem," the report said.

"In October 2018, the interior minister stated that the whereabouts of more than 37,400 people who had gone missing since 2006 remain unknown.

"According to the CNDH (National Human Rights Commission), more than 3,900 bodies have been found in over 1,300 clandestine graves since 2007."

On Monday, heavily armed cartel members ambushed three cars packed with women and children on a highway in northern Mexico.

Rhonita Miller, 30, Dawna Langford, 43, and Christina Langford Johnson, 29, died in a hail of gunfire, according to relatives.

The slain children have been identified as Howard Miller, 12; Trevor Langford, 11; Krystal Miller, 10; Rogan Langford, two; and eight-month-old twins, Titus and Tiana Miller.

Ms Miller's burnt-out, bullet-ridden SUV and the two other vehicles were reportedly found outside the town of Bavispe. Several other children were shot and injured in the attack but survived after fleeing and hiding in bushes nearby.

The victims were all US citizens who lived in La Mora, a decades-old settlement in Sonora near the US border, about 112km south of Douglas, Arizona.

Earlier, news.com.au revealed they were members of the Fundamentalist Church of Jesus Christ of Latter-Day Saints (FLDS), a polygamous sect that split from the mainstream Mormon church.

They fled to Mexico and Canada to avoid legal consequences when the practice was banned at the turn of the last century.

Willie Jessop, who is related to one of the victims, was once one of the highest profile FLDS members — with the exception of its infamous prophet turned convicted paedophile, Warren Jeffs.

FLDS member Taylor Langford, who splits his time between the Sonora settlement and Utah, said the three women killed were is aunt and two cousins.

His father and uncle, who were both in Mexico when the attack took place, told him each woman was driving a separate car when they were ambushed on a quiet dirt road they often travelled without problems.

He said Rhonita Miller, and her four children, including 8-month-old twins, were travelling about six km behind the other vehicles when their car was struck by gunfire and engulfed in flames.

The gunmen then attacked the other cars, one carrying Christina Langford Johnson and her baby and the other carrying Dawna Langford and nine children. He said several children survived, including a 9-year-old girl who was shot in the arm and found hours later.

Ms Miller's father, Adrian LeBaron, said in a brief telephone conversation from Sonora state that the family had requested help from the Mexican government but had not yet heard back. He spoke during a break providing information to authorities at the medical examiner's office.

"She was fired at, all shot up, burned," Mr LeBaron said of his daughter.