Authorities are working to identify the cause of a partial ferry dock collapse on Georgia’s Sapelo Island that turned a day of celebration into tragedy, leaving at least seven dead and six critically injured as crowds gathered for a cultural festival.

Icy Whites family was among hundreds visiting the isolated Georgia barrier island Saturday for a fall festival spotlighting the history and culture of its tiny Gullah-Geechee community of Black slave descendants. The celebration gave way to tragedy when the gangway collapsed, sending seven visitors to their deaths.

ATLANTA — National civil rights attorney Ben Crump is demanding a federal investigation into the deadly dock collapse on Sapelo Island this past weekend. Crump is representing the families of three people who died and one person who was hurt. Investigators are still working to figure out why the ferry deck collapsed on Saturday.