SAVANNAH, Ga. ‒ "Catastrophic failure" was blamed Sunday for the collapse of a dock gangway that killed seven people and plunged more than a dozen others into murky waters, bringing tragedy to a cultural festival on historic Sapelo Island.

At least seven people are dead after a portion of a ferry dock collapsed at about 3:50 p.m. Saturday on Sapelo Island, authorities say. Twenty people fell into the water when a gangway to the dock collapsed, said Tyler Jones, a spokesman for the Georgia Department of Natural Resources, which operates the dock.

Investigators, including a team of engineers and specialists, are now on the scene to determine what caused the sudden collapse.

Georgia authorities announced Sunday an investigation has been opened into the "catastrophic failure" of the dock gangway.

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.