Jeff Bush, 37, was in his bedroom on Thursday night when the earth opened and took him and everything else in his room. Five other people were in the house but escaped unharmed. Mr. Bush's brother jumped into the hole to try to help, but he had to be rescued by a sheriff's deputy.
Engineers returned to the property on Saturday morning to do more tests after taking soil samples and running tests there all day Friday. They said the entire lot was dangerous, and no one was allowed in the house.
"I cannot tell you why it has not collapsed yet," said Bill Bracken, the owner of an engineering company called to assess the sinkhole. He described the earth below as a "very large, very fluid mass."
"This is not your typical sinkhole," said Michael Merrill, the Hillsborough County administrator. "This is a chasm. For that reason, we're being very deliberate."
The hole had grown to 20 feet deep and 30 feet wide by Friday night, and officials said it was still expanding and "seriously unstable."
Officials delicately addressed another sad reality: Mr. Bush was likely dead, and the family wanted his body.
"They would like us to go in quickly and locate Mr. Bush," Mr. Merrill said.
Two neighboring houses were evacuated, and officials were considering further evacuations. Members of the media were moved from a lawn across the street to a safer area a few hundred feet away.
"This is a very complex situation," said the Hillsborough County fire chief, Ron Rogers. "It's continuing to evolve, and the ground is continuing to collapse."
Sinkholes are so common in Florida that the state requires home insurers to provide coverage against the danger. While some cars, homes and other buildings have been devoured, it is extremely rare for a sinkhole to swallow a person.
Florida is highly prone to sinkholes because of the underground prevalence of limestone, a porous rock that easily dissolves in water, creating caverns.
"You can almost envision a piece of Swiss cheese," Taylor Yarkosky, a sinkhole expert from Brooksville, Fla., said while gesturing to the ground and the sky-blue house where the earth opened in Seffner. "Any house in Florida could be in that same situation."
A sinkhole near Orlando grew to 400 feet across in 1981 and devoured five cars, most of two businesses, a three-bedroom house and the deep end of an Olympic-size swimming pool.
More than 500 sinkholes have been reported in Hillsborough County alone since the government started keeping track in 1954, according to the state's environmental agency.
The sinkhole that swallowed Mr. Bush caused the home's concrete floor to cave in around 11 p.m. Thursday as everyone in the Tampa-area house was turning in for the night. It gave way with a loud crash that sounded like a car hitting the house and brought Mr. Bush's brother, Jeremy, running.
Jeremy Bush said he had jumped into the hole but could not see his brother before the ground crumbled around him. A sheriff's deputy reached out and pulled him to safety.
"The floor was still giving in and the dirt was still going down, but I didn't care — I wanted to save my brother," Jeremy Bush said through tears Friday in a neighbor's yard. "But I just couldn't do nothing."
