A young girl was buried in sand and died when a deep hole she was digging with a little boy collapsed on them both at a south Florida beach, authorities said.

Emergency crews responding at around 3pm to Lauderdale-by-the-Sea found the boy, who is about eight years old, buried up his chest in sand, said Sandra King, a spokesperson for Pompano Beach Fire Rescue.

The girl, about seven years old, was completely buried underneath the boy, Ms King told the South Florida Sun-Sentinel.

Investigators on the Florida beach
Investigators on the Florida beach (Mike Stocker/South Florida Sun-Sentinel via AP)

The hole was five or six feet (1.8 meters) deep when the collapse happened, she said.

Rescuers used support boards to keep more sand from collapsing in as they used shovels to dig the children out, Ms King said. She did not know how long they were buried.

The girl was rushed to Broward Health Medical Centre in Fort Lauderdale, where she was pronounced dead, Ms King said. The boy was admitted to hospital in stable condition.

It was not immediately known whether an adult was helping the children dig the hole.