SAPELO ISLAND, Ga. -- Authorities in Georgia are responding to a deadly gangway collapse at a dock on Sapelo Island.

The Georgia Department of Natural Resources responded with local, state and federal agencies to the Marsh Landing Dock on the island, where at least 20 people went into the water when the collapse occurred. As of about 8 p.m., authorities said they believed seven people had died.

Authorities didn't know how many more were injured but said the gangway had been secured, and an investigation is underway. A spokesperson for the DNR told the Associated Press that several people were taken to area hospitals. The AP reports other agencies, including the U.S. Coast Guard, were on hand searching for survivors.

The state-managed island is located in the barrier island chain between the Savannah and St. Marys rivers on the Georgia coast and is only accessible by ferry. The island is also the home of the Sapelo Island National Estuarine Research Reserve, the University of Georgia Marine Institute and the Hog Hammock community of about 70 residents.

The AP reports the collapse happened as crowds gathered on the island for a celebration of this Gullah-Geechee community - many of them descendants of slaves.