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.

Georgia Department of Natural Resources Commissioner Walter Rabon said Sunday morning that at least 40 people were on the gangway and that half fell into the water. The dock gave way before 4 p.m. in a "catastrophic failure," prompting a response from the Coast Guard and state and local agencies.

The "catastrophic failure" of an aluminum ferry gangway caused the deaths Saturday of seven people who were attending an annual cultural event on historic Sapelo Island off the coast of Georgia, officials said Sunday.

Investigators have begun looking for reasons behind the failure at a ferry dock on Sapelo Island, the site of a festival celebrating the heritage of descendants of enslaved people.

Officials were on location in Georgia Sunday investigating the collapse of a ferry dock gangway that left seven people dead and six others critically injured Saturday.

Georgia authorities say they are investigating the “catastrophic failure” of a dock gangway that collapsed, killing seven on Sapelo Island.

The gangway collapsed Saturday as festival goes prepared to board a ferry amid Sapelo Island's annual Cultural Day, officials say.

A crowd had gathered for a celebration of the Gullah Geechee people, who have inhabited Sapelo Island since enslaved people were forcibly brought from Africa to the U.S.

ATLANTA − At least seven people were killed after part of a boat dock collapsed, sending at least 20 into the Atlantic waters off the coast of Georgia on Saturday. U.S. Coast Guard ships were searching through the night for missing people.