Two teenage boys wave goodbye to their mothers across a field in rural Mexico, leaving home in search of the American dream. The opening moments of the Mexican film-maker Fernanda Valadez’s Identifying Features, available to stream from this week, reflects scenes played out every day across Mexico and Central America, as men, women and children journey north in search of safety and job opportunities.

Valadez, 39, starts her directorial debut film in her home state of Guanajuato – a picturesque, once tranquil state in the centre of the country. In recent years Guanajuato has fallen victim to the evolving geography and relentless nature of Mexico’s humanitarian crisis; it is now one of the most dangerous places in the country for those who live there and for people travelling through on the migrant trail.

The inspiration for the film’s central story is based on a real-life account published in the Blog del Narco – an anonymous blog detailing crimes of kidnappings or gun battles that local newspapers were warned off reporting.

The film starts by accompanying two teenage boys as they travel towards the border. The bus they are on is intercepted by armed men who kill most of the passengers. One of the boys, Jesús, is spared after agreeing to work for the cartel. First he must kill his friend and burn the bus.

Throughout the film Valadez combines mystical realism with unflinching reality. The red fire that engulfs the bus and its passengers evokes hellfire, a fantastical force of evil.

Valadez says she wanted to do something different with Identifying Features, creating “not just another Latin American film about concepts and social interest”. Instead of adopting the narrative documentary style chosen by many other film-makers to depict the perils of the migrant journey through Mexico, she has crafted a horror film.

“By using more metaphoric figures like the devil to express the violence we felt able to take the audience very close emotionally,” says Valadez, in an interview.

Yet, the scenarios that Valadez shows us are real. Scores of buses carrying migrants are believed to have been ambushed in this way in recent years, arriving at their final destination with no passengers, only their luggage. In 2010, 72 migrants from Central and South America who had been abducted from several buses were massacred in the northern state of Tamaulipas by members of the Los Zetas cartel after refusing to pay a ransom or take jobs as hitmen. Only three people survived.

Another character, Jesús’s mother, Magdalena, embarks on a journey of her own, following in the footsteps of her son from their village in Guanajuato to find out what happened to him. Magdalena’s grief and steely determination are counterpoints to the cartel violence that lurks behind every corner.

“The key word is empathy,” says Valadez. “Empathy is the bridge from which art in general begins, it’s so important to storytelling in films. It’s what has taken this film to audiences we never expected. Empathy is the key to igniting conversations.”

People on the migrant trail are not the only ones at risk of disappearing in Mexico. The film includes the story of a surgeon whose son had disappeared four years earlier while driving to see friends in Monterrey in Nuevo León, a state where forced disappearances were once so widespread that billboards instructed residents to call the armed forces in case of an emergency as the police were in cahoots with the criminal gangs.

“At first kidnappings were something you read about happening to migrants, but within a couple of years [of the launch of the war against drugs] it started happening closer to home, closer to cities and to the middle classes,” says Astrid Rondero, who co-wrote and produced Identifying Features.

“When we were teenagers [in Mexico City] you could no longer take a trip on the highway to the beach in case the bus was kidnapped. Anyone could be in the wrong place at the wrong time,” she says.

At least 73,000 people have gone missing since the start of the militarised war on drugs in 2006, while at least 39,000 unidentified bodies are unclaimed in morgues. This war without an end has so far cost the lives of at least 300,000 Mexicans.

Identifying Features offers up no hope of resolution or an end to the desperate search of families for their loved ones.

“[With this film] we went to the dark side because we are still in this crisis, there is no closure. There was hope of change with the new government of [Andrés Manuel] López Obrador but now it’s out of control, the stories may be even more gruesome,” says Rondero. “The ending is dark because we’re still in that place, it feels like a complete betrayal.”

The current administration agreed to Donald Trump’s demands to place thousands of asylum seekers on the Mexican side of the border, where they have been subjected to violence, extortion, kidnap and inhumane living conditions, according to Human Rights Watch. Now, at the behest of the Biden government, more troops are being deployed to Mexico’s southern border to stop migrants and refugees crossing.

Amid daily reports of atrocities which only seem to get worse, the film-makers believe that art plays a crucial role in evoking empathy and political consciousness among those numbed by the pain.

“When we show the film here in Mexico, the emotional information helps people to finally start understanding what we’ve been living since 2000,” says Rondero. “We cannot allow this to happen, and we have to do something to change it because it’s not normal for so many people to be travelling on dirt roads looking for their loved ones.”

• Identifying Features is available to stream on BFI Player.