Jessica Damico, a spokeswoman for Hillsborough County Fire Department, said first responders had been unable to make contact with the 34-year-old man, who was presumed dead. She stressed his death had not been confirmed.
Damico said firefighters were called to the house in Brandon just after 11 p.m. Thursday and said more equipment was being brought to the scene.
She said the scene was unstable and that rescuers had been unable to get close because of the danger.
Damico said that the sinkhole was 30 feet across at the surface, but said engineers had estimated that below the surface it could be 100 feet wide, and 50 feet deep.