In May 2021, fishermen in Tobago discovered a boat filled with more than a dozen bodies. No one knew who they were; no one knew where they had come from. Over a two-year investigation, reporters at the Associated Press went looking for their identities to tell a story about lives shaped by inhumane forces and lost at sea.

The vessel that reached Tobago was registered in Mauritania, a large and mostly deserted country in northwest Africa nearly 3,000 miles (4,800 km) away. Evidence found on the boat — and its style and color as a typical Mauritanian “pirogue”— suggested the dead were likely African migrants who were trying to reach Europe but got lost in the Atlantic.

In 2021, at least seven boats appearing to be from northwest Africa washed up in the Caribbean and in Brazil. All carried dead bodies.

These “ghost boats” — and likely many others that have vanished — are in part an unintended result of years of efforts and billions of dollars spent by Europe to stop crossings on the Mediterranean Sea. That crackdown, along with other factors such as economic disruption from the pandemic, pushed migrants to return to the far longer, more obscure and more dangerous Atlantic route to Europe from northwest Africa via the Canaries instead.

Arrivals on the Atlantic route jumped from 2,687 in 2019 to more than 22,000 two years later, according to Spain’s Interior Ministry. But for those to arrive, many more must have departed, said Pedro Vélez, an oceanographer at the Spanish Institute of Oceanography. Vélez wasn’t surprised to learn of migrant boats appearing in the Caribbean – that is where floating devices dropped by scientists on the West African coast naturally drift.

“The sea conditions there are extremely harsh,” he said. “Extremely harsh.”