Another 55 people, all Haitians, were fished out of the water about 100 meters from the shore, said the U.S. Coast Guard, which assisted in the rescue.
Colin Farquhar, commissioner of the Royal Turks and Caicos Islands Police Force said it had detained 33 people on suspicion of migrating illegally, who "will be repatriated to Haiti at the earliest opportunity."
Farquhar did not say what came of the other 22 people reported rescued.
The Turks and Caicos Government said the boat, an overloaded sail freighter, had been halted by marine police around 3 a.m. Wednesday. While it was being towed to dock, the boat tipped over, dumping its passengers into the water.
"The stricken vessel has now been removed from the water and will be central to our ongoing investigations into this matter," Farquhar said. "We must all remain vigilant to combat illegal migration."
He added the search, rescue and recovery missions had been halted late Wednesday as darkness fell over heavy seas. Police were also searching for "the handful of people who reached shore and fled the scene."