At least seven people were killed on Saturday when a ferry dock gangway collapsed on a Georgia island where hundreds had gathered to celebrate the heritage of a community of slave descendants, the authorities said.

The deaths on Sapelo Island were confirmed by the Georgia Department of Natural Resources, which manages the island and operates its ferry service. The island is about 70 miles by road south of Savannah, Ga.

The department said late Saturday that at least 20 people went into the water when the gangway collapsed, and that it was not immediately clear how many people had been injured. A spokesman for the U.S. Coast Guard in Savannah said by phone that he was unable to confirm the injury toll.

Hundreds of people visited Sapelo Island on Saturday to attend an annual festival that celebrates the heritage of the Gullah Geechee people, said Griffin Lotson, the mayor pro-tempore of the nearby city of Darien, Ga. It was not clear early Sunday if any of those visitors had been victims of the accident.

The Gullah Geechee, who live along the coasts of the Carolinas, Georgia and northern Florida, are descendants of enslaved West African people who were brought to the southeastern United States more than two centuries ago. The Sapelo Island festival honors their language, cuisine and art, said Mr. Lotson, a seventh-generation Gullah Geechee.

“The day is about all of the culture,” he said by phone late Saturday. “From Africa, to the way that it was on the plantation, to the 21st century with the young folks and what they do.”

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