It was 2011 when Italian photojournalist Max Hirzel first started thinking about the identification of migrant bodies. He was working on a project in Mali when he met a young man named Alpha, who told him about a grave he’d seen in the desert of a girl from his native Cameroon. Alpha wondered if her parents and siblings knew she was there, adding that this scared him more than death itself: the idea of being buried alone in a graveyard where no one could mourn him.

The project began in earnest in 2015, when Hirzel started touring cemeteries in Sicily to photograph migrants’ graves. Then, on 18 April, the deadliest modern shipwreck in the Mediterranean happened: a vessel carrying between 700 and 1,100 people sank between Libya and Italy; only 28 survived. Matteo Renzi, the Italian prime minister at the time, vowed to salvage the ship in an effort to identify the bodies and give them a proper burial, and the vessel – now known as “the boat of innocents” – was pulled to the surface in June 2016.

The bodies on board were taken to a Nato base in Melilli, Sicily, where forensic doctors performed autopsies; further testing was done at the Labanof laboratory in Milan by a team of pathologists, many of them very young, led by Dr Cristina Cattaneo. The lengthy and laborious process involved cataloguing objects and documents found on the victims, and, where possible, comparing post-mortem samples with items provided by the families.

Gravestones in the cemetery of Rosolini in Sicily mark the burial places of six victims of an 18 April 2015 shipwreck who were identified as part of the Melilli Nato base project. Photograph: Max HIrzel

Hirzel documented this process and others like it in his series Migrant Bodies. “In Italy, there’s no standard protocol for dealing with bodies recovered at sea – the judicial authorities at local level make their own arrangements,” he says. “This kind of work is done very rarely.” Renzi’s decision to recover the boat was controversial, with critics questioning the €9.5m spent. Hirzel wanted to show the value of these efforts: the series felt like a duty, he says, to victims and their families.

As part of the project, Hirzel travelled to Senegal, where he met the family of Mamadou; he had been missing for two years and is thought to have been one of the victims of the 18 April sinking. “People in Italy say: ‘Why should we spend all this money when no one is looking for them?’” says Hirzel. “But Mamadou’s family had been looking for him, in their own way: his brothers visited holy men in Gambia and Senegal to find out what had happened to him. Everybody is waiting.” Red Cross psychologist Miriam Orteiza said to Hirzel: “It’s impossible for families to face their grief until there’s a body, until there is certainty. This is why it’s important.”

In Syracuse, Sicily, police officer Angelo Milazzo spent months working on the case of a migrant shipwreck that occurred in August 2014. He set up a Facebook page to share material with families, and eventually identified 23 out of 24 bodies. “One of these was Bilal,” says Hirzel, “the 16-year-old brother of Mohamed Matok. Angelo and Mohamed spoke for years over email and Whatsapp, using Google Translate, and they became friends.” Matok obtained a visa to come from Damascus to pray over his brother’s grave; Hirzel photographed the visit. “When he met Angelo at the airport they embraced, and Mohamed said to me: ‘Angelo is an angel. Knowing where my brother is, being able to pick up his belongings – what he did for me was so important.’”

Hirzel’s photographs will be on show at Sink Without Trace, the first UK exhibition to focus specifically on the more than 30,000 migrants who have drowned in the Mediterranean over the past 30 years. It will feature work from 18 artists from 10 countries, including seven who migrated by sea as refugees. “It’s a subject that’s hardly dealt with in galleries here,” says artist Maya Ramsay, who curated the exhibition with Federica Mazzara, senior lecturer at the University of Westminster. “Part of me wonders whether it’s partly to do with a sense of culpability, that we’re not doing anything about the subject, that we’re partly responsible. It’s a really difficult subject. It’s not easy for anybody – not for the artists or the viewers.” Apart from raising money for rescue charity AlarmPhone, Ramsay hopes “people will be inspired to do something”.

Nikolaj Bendix Skyum Larsen: End of Dreams 2015. Larsen is a Danish artist based in Paris. His work features in the exhibition Sink Without Trace.

The show will provide a counterpoint to the controversial Barca Nostra (Our Boat), in which a team led by Christoph Büchel, a Swiss-Icelandic artist, exhibited the recovered “boat of innocents” – the same boat that the bulk of Hirzel’s project focuses on – at this year’s Venice Biennale. “Putting the boat on display without any background context is not what I would have done,” says Ramsay. “I find it a lost opportunity for telling people more about what happened – and what does still happen for lots of boats.”

Hirzel feels similarly: “When you pass from information to a form of celebration, there’s a risk that it becomes a monument of sorts to European compassion: so that we can feel sympathetic, getting emotional in front of this boat. But the next day, 40 people died at sea. I feel the artist acted in good faith but, considering the situation, if I was a survivor or a family member watching Europeans take selfies with that boat… I’d be annoyed.”

Annex: IMO circular #11 (detail), 2012, one of a series of paintings by Mario Rossi made on print-outs from International Maritime Organisation reports of ‘unsafe practices associated with the trafficking or transport of migrants by sea’. Photograph: Mario Rossi

Reminding Europe of its responsibility is central to Hirzel’s work. “We should be ashamed. We’re hypocrites – talking about human rights, calling it ‘the boat of innocents’. But if they had survived we would have called it ‘the boat of illegal immigrants’. They’re just doing what people have done for all of humanity – when they need to, they move. For me this can never be illegal. We treat these events as if they were natural disasters, but it’s not normal for kids aged 22 or 23 to be conducting autopsies on bodies the same age as them, in these quantities. I feel like if there had been a will to resolve this we would have found a way by now.”

Hirzel hopes his images will act as testimony. “Maybe one day these photos will be used to assess our current societies. At least no one will be able to say they didn’t know what was happening – this is proof.” Death, he adds, is something that connects us all. “We’ve seen a lot of coverage of migration, but this is an angle that touches us as humans. Grief, death – this is something we all have in common.”

Sink Without Trace will be at P21 gallery, London NW1, from 13 June to 13 July