Authorities are searching the Caribbean for 28 people missing from a boat that left Venezuela and appears to have sunk, after four bodies and wreckage washed ashore in nearby Curacao, officials said Thursday.

It remained unclear why the boat sank as it headed to the Dutch island, a journey frequently taken by people fleeing Venezuela's economic collapse.

The boat carrying 34 people departed Tuesday night, Venezuela's Regional Civil Protection director Jose Montano said, adding that two people managed to swim safely to shore in Curacao, which is about 45 miles (70 kilometers) away at its closest point.

He said Venezuelan authorities learned of the incident after relatives of one passenger called for help.

Police on the island Wednesday morning discovered the bodies of two men and two women on shore, said Curacao police spokesman Reginald Huggins, adding that the investigation is ongoing.

"We also found a lot of wood that's from a boat," he said, adding that debris included gas cans and personal belongings.

The victims have not been identified, and Huggins said it was unclear whether the two men who made it safely to shore were on the same boat or another. He said they were in police custody.

Curacao's police and coast guard continued their search by land and air, looking for possible survivors or victims, he said.

Luis Stefanelli, a member of Venezuela's congress, said passengers of the small boat were all under the age of 35.

The incident comes amid heightened tensions after Venezuela's President Nicolas Maduro on Friday ordered a trade blockade with Curacao, Aruba and Bonaire, suspending sea and air travel.

Venezuelan authorities allege the smuggling of products out of Venezuela to neighboring countries is one of the causes of the severe shortage of food and other basic products that the South American country has been facing for several years.