SAN JUAN, Puerto Rico (AP) — A boat loaded with suspected migrants capsized north of an uninhabited island near Puerto Rico and 11 people had been confirmed dead while 31 others were rescued Thursday, authorities said.

It wasn’t immediately clear how many people were aboard the boat when it turned over, said US Coast Guard spokesman Ricardo Castrodad. He said a “mass rescue effort” was still underway.

“We’re looking to rescue as many people as we can and find as many survivors as we can,” he said.

At least eight Haitians were taken to the hospital, although the nationalities of all those aboard the boat were not immediately known.

A US Customs and Border Protection helicopter spotted the overturned boat late Thursday morning.

“If not for that, we would not have known about this until someone would have found any sign or received reports from people that their loved ones are missing,” Castrodad said. “They found them early enough that we were able to coordinate a response.”

The boat was spotted more than 11 miles (18 kilometers) north of the uninhabited island of Desecheo, which is off Puerto Rico’s west coast.

The incident was the latest in a string of capsizings across the region as migrants from Haiti and the Dominican Republic flee violence and poverty in their countries.

On Saturday, the US Coast Guard and Dominican navy rescued 68 migrants in the Mona Passage, a treacherous area between Puerto Rico and the Dominican Republic. One woman believed to be from Haiti died, Castrodad said.

“These voyages are dangerous,” Castrodad said. “They’re unsafe, they are grossly overloaded … (and) no lifesaving equipment. It wouldn’t really take much for any of these vessels to capsize.”

From October 2021 to March, 571 Haitians and 252 people from the Dominican Republic were detained in waters around Puerto Rico and the US Virgin Islands, according to US Customs and Border Protection. The majority of those Haitians, 348 of them, landed in Puerto Rico’s uninhabited Mona Island and were rescued.

In fiscal year 2021, 310 Haitians and 354 Dominicans were detained, compared with the 22 Haitians and 313 Dominicans apprehended in fiscal year 2020.

Meanwhile, the US Coast Guard said that in the fiscal year that ended Sept. 30, it apprehended 1,527 Haitians, 838 Cubans and 742 people from the Dominican Republic in the region, which includes Florida and the Caribbean.

Since then, trips of human smuggling boats have only increased, authorities say.

In January, the Coast Guard searched for at least 38 people missing off Florida’s coast after a suspected human smuggling boat that had left the Bahamas capsized in a storm. A sole survivor was reported.

Hundreds of Haitians have arrived in Florida alone in recent months after swimming ashore.

Haiti is struggling with a surge in gang-related violence that has killed dozens of people, including women and children, and caused thousands of families to flee their homes. Kidnappings also have spiked, including those of eight Turkish citizens who on Sunday were forced off a bus they had boarded in the Dominican Republic.

Kidnappings in the country of more than 11 million people have increased 180% and homicides are up 17% in the past year, according to the United Nations, which last week expressed concern over “the rapid deterioration of security and human rights” in Haiti.

Many have criticised the administration of US President Joe Biden for deporting more than 20,000 Haitians in recent months given the country’s deepening turmoil.