At least 20 people are still missing after a ship carrying Cuban migrants sank off the coast of Florida on Wednesday, Reuters reports, per U.S. Border Patrol. The boat sank on account of inclement weather caused by Hurricane Ian, the first hurricane to threaten Florida since 2018.

Four individuals on the boat were able to swim to shore and have since been hospitalized, Reuters adds, per officials and local media. The U.S. Coast Guard initiated a search and rescue operation for the others and was able to locate three of the original missing 23 migrants.

Hurricane Ian swept through Cuba on Tuesday, killing at least two. The storm then swept toward Florida’s southwestern coast, where it made landfall Wednesday afternoon.

“You need to get into the interior of your home and begin to brace for a period of sustained damaging, potentially devastating winds,” said acting National Hurricane Center Director Jamie Rhome, as quoted by the Orlando Sentinel. “Do not venture outside at all. do not try to evacuate at this point. You really have to get into the interior of your house and ride this part out.”

As of 3:30 p.m. ET on Wednesday, over 800,000 people in Florida were without power, “mostly in Collier, Charlotte, Lee, Sarasota, Manatee, Miami-Dade, Broward, Palm Beach, Hillsborough, and Pinellas counties,” the Sentinel writes. 

Ian is considered a high-end Category 4 hurricane, with winds near 150 mph. The storm is predicted to move “northeastward, crossing [Florida] diagonally before moving offshore somewhere between Cape Canaveral and Jacksonville,” CNN reports.