Authorities in the eastern Caribbean nation of St. Kitts and Nevis said Thursday they are investigating the circumstances that led to the discovery of at least 19 bodies found drifting at sea.

At around 11:30 a.m. on Wednesday the St. Kitts and Nevis Coast Guard responded to a report of a drifting vessel off the coast of Nevis. The partially submerged boat contained decomposed human remains. It was towed to St. Kitts, where police and medical officials are conducting investigations.

“It was a fishing vessel, which is not typically found in the Caribbean,” Police Commissioner James Sutton told The Associated Press. “We are not certain, but we believe that this vessel originated off the West African coast.”

Sutton said officials now face the difficult task of determining the exact number of bodies and identifying them. The advanced state of decomposition, he said, has made it difficult.