At least 9 people are dead, including one infant, after an overloaded boat apparently carrying Haitian migrants sank off the coast of Florida.

Coast Guard Capt. James Fitton said 16 people had been rescued, but a search was under way for more.

Authorities weren't sure how many were aboard the boat, but they believed around 30 were dumped into the sea near Miami Beach.

The accident appears to have happened during a migrant-smuggling trip, officials said. They didn't know if the boat had capsized or crashed. The vessel has not been found, and is thought to have sunk because it hasn't been spotted from the air.

"The boat was obviously overloaded," Fitton said. "It's a tragedy that someone would be so callous with human life."

The vessel apparently left Bimini in the Bahamas on Tuesday night. It was believed to have flipped at about 2 a.m., but officials didn't learn about it until another boater called more than 10 hours later.

The boater reported pulling three people from the water and said about 25 others were awaiting rescue.

Fitton said all those saved were expected to recover. Children and women were among those aboard, including a pregnant woman.

Two helicopters, a jet and three boats helped in the rescue effort about 15 miles off the shore of Miami Beach, where water temperatures were in the high 70s Wednesday afternoon.

Since October, the Coast Guard says that it had stopped 1,377 Haitians, up from 972 during the same seven-month period last year.

The Rev. Luke Harrigan, a Fort Lauderdale pastor who ministers to the Haitian-American community, was working with the Coast Guard to help the victims.

He said Haitians, who live in the Western Hemisphere's poorest nation, are known to pay $2,000 to $4,000 to be smuggled into the U.S.

Four tropical storms and hurricanes battered the country during last year's harvest season, killing 793 people, crippling agriculture and causing $1 billion in damage to irrigation, bridges and roads.

In January, United Nations-sponsored groups said more aid was urgently needed to stave off famine in several areas of the country.

"The economic conditions in Haiti are deplorable, and I don't see them getting any better any time soon," said Andy Gomez, a University of Miami expert on Caribbean migration. "And the Haitian-American community has developed a pretty good network here in the last five or 10 years, just as the Cuban-Americans have done, so there's more of a reason to come."

The Coast Guard said it was not known whether the boat's captain and any crew members were among those found, and survivors haven't indicated who may have organized the trip.

"We haven't even asked those questions yet," Fitton said.

The Associated Press contributed to this report.