Authorities are investigating 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.

Seven people died after a ferry gangway collapsed Saturday in Georgia, according to state officials. Authorities were still working Sunday to determine what caused the collapse. The facts The aluminum gangway should have been able to handle the 40 or so people on it before “a catastrophic failure,

The aluminum gangway suffered structural failure as historic Sapelo Island hosted an event celebrating its Gullah Geechee history and culture.