The state Department of Natural Resources is investigating what led to boat dock collapse on Sapelo Island that ended with seven people being killed.

On Saturday around 4:30 p.m., multiple state, local and federal agencies, including help from Liberty County, responded to call about a collapse of a gangway at the Sapelo Island Marsh Landing Dock.

At least 20 people were thrown into the water when the gangway collapsed. Six others were critically injured, and two were flown to hospitals for further treatment, according Capt. Chris Hodge of the DNR.

“We are conducting an investigation,” Capt. Hodge said. “It will be ongoing for some time to determine the cause of this incident.”

The Sapelo Island Cultural and Revitalization Society was holding its annual Cultural Day on Sapelo, annually its biggest event in celebration of the Gullah-Geechee heritage.

Georgia DNR and multiple other emergency agencies deployed boats, equipped with side-scan sonar, and helicopters for search and rescue missions. Georgia DNR will continue to work in coordination with local, state, and federal agencies, including Georgia State Patrol, McIntosh County Sheriff’s Office, McIntosh County Fire Department, and U.S. Coast Guard, among others.