A 6-year-old Cuban boy died early Thursday after the speedboat he was being smuggled on capsized as the U.S. Coast Guard tried to intercept it, trapping him underneath, authorities said.

The other 30 people in the boat were rescued.

"This terrible incident is an example of the dangers inherent to illegal entry to the United States by sea," Rear Adm. D. Brian Peterman, commander of the Seventh Coast Guard District, said in a statement.

The 33-foot boat initially spotted on radar about 45 miles south of Key West just before 1 a.m. The Coast Guard cutter Dauntless pursued the vessel, but the boat refused orders to halt and was maneuvering erratically in an attempt to get away, the Coast Guard said.

The Dauntless lost sight of the boat briefly, then found it capsized with 30 people clinging to the hull. The 30 were rescued by two other boats and the cutter, and it was learned that the boy was missing. His body was found when the cutter's crew overturned the boat, authorities said.

Immigration and Customs Enforcement officials were investigating.

Officials said the quality of the boat makes it clear that it was a smuggling operation and not a group of Cubans trying to leave the communist island (search) without help.

"Small boats, very fast, trying to evade us — that's typical with what we see when we're dealing with migrant smugglers," Coast Guard Petty Officer Ryan Doss said. "We don't see these types of boats leaving Cuba unless they're smuggling."

The 30 survivors were being held aboard the Dauntless until a decision is made whether to return them to Cuba. It was not known if the boy's parents were among the survivors. Under the U.S. government's "wet-foot, dry-foot" policy, immigrants intercepted at sea are usually returned while those who make it to land are generally allowed to stay.

The U.S. government has prosecuted smugglers for the deaths of Cubans at sea. The Coast Guard was trying to determine if any of those rescued were the smugglers.