Authorities say they’ve recovered multiple bodies after a rock formation collapsed on leisure boats in southeastern Brazil.

According to Reuters, the tragedy occurred Saturday on Furnas Lake in the state of Minas Gerais. Video shows several boats floating near a waterfall as a slab of rock begins to break off from a cliff. The formation reportedly fell directly onto a couple of boats, leaving at least six people dead and nine others seriously injured. Authorities say they are searching for 20 individuals who they believe are missing. 

“We are all stunned, nobody knows how many victims, but I can already tell you that there were not one or two deaths, but many deaths,” resident Rovilson Teixeira told Brazilian outlet OTempo. “There are a lot of hurt people. The region is full of ambulances that have come from other areas to pick up the victims, but no one yet realizes the scale of the tragedy here.”

Those who sustained serious injuries have been since been hospitalized with broke bones as well as head and facial injuries. Reuters reports nearly two dozen others were treated for “light injuries.”

Emergency personnel continue to search for the missing individuals. It’s reported that each boat was carrying between 12 to 20 people, including some children. Officials have yet to publicly identify the victims.

Officials said they believe heavy rainfall contributed to the collapse, as the area has recently endured severe flooding that has forced some residents to leave their homes. The Brazilian Navy is reportedly investigating the matter.