Engineers worked gingerly Saturday morning to find out more about a slowly growing sinkhole that swallowed a Florida man in his bedroom, believing the entire house could eventually succumb to the unstable ground, as well as homes next door.

Jeff Bush, 37, was in his bedroom Thursday night when the earth opened and took him and everything else in his room. Five other people were in the house but managed to escape unharmed. Bush's brother jumped into the hole to try to help, but he had to be rescued himself by a sheriff's deputy.

On Saturday, Hillsborough County Fire Rescue spokesman Ronnie Rivera said one of the homes next door to the Bush house also was compromised by the sinkhole, as determined through testing. The family, which had evacuated Friday, would be allowed to go inside for about a half-hour to gathering belongings, Rivera said. The family was outside, crying and organizing boxes.

Engineers had been testing since 7 a.m. Saturday local time. By 10 a.m., officials moved media crews farther away from the Bush house so experts could perform tests on the home across the street.

It's unclear how large the sinkhole is or whether it leads to other caverns and chasms throughout the neighbourhood. Experts say the underground of West Central Florida looks similar to Swiss cheese, with the geography lending itself to sinkholes.

Experts spent the previous day on the property, taking soil samples and running various tests — while acknowledging that the entire lot where Bush lay entombed was dangerous. No one was allowed in the home.

"I cannot tell you why it has not collapsed yet," Bill Bracken, the owner of an engineering company called to assess the sinkhole, said of the home. He described the earth below as a "very large, very fluid mass."

"This is not your typical sinkhole," said Hillsborough County administrator Mike Merrill. "This is a chasm. For that reason, we're being very deliberate."

Jeremy Bush, brother of Jeff Bush, tried to rescue his brother Jeff as a sinkhole opened up underneath the bedroom and swallowed him up. (Chris O'Meara/Associated Press)

Officials delicately addressed another sad reality: Bush was likely dead and the family wanted his body. Merrill, though, said they didn't want to jeopardize any more lives.

"They would like us to go in quickly and locate Mr. Bush," Merrill said. Officials added Saturday morning that a fund had been set up to help the families affected by the sinkhole.

On Saturday, Jeremy Bush — who tried to rescue his brother when the earth opened — lay flowers and a stuffed lamb near the house and wept.

Hillsborough County Fire Chief Ron Roger called the situation "very complex."

"It's continuing to evolve, and the ground is continuing to collapse," he said.

Sinkholes are so common in Florida that state law requires home insurers to provide coverage against the danger. While some cars, homes and other buildings have been devoured, it's extremely rare for them to swallow a person.

Florida like 'a piece of Swiss cheese'

Florida is highly prone to sinkholes because there are caverns below ground of limestone, a porous rock that easily dissolves in water.

"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 home 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 sports cars, most of two businesses, a three-bedroom house and the deep end of an Olympic-size swimming pool.

'The dirt was still going down, but I didn't care. I wanted to save my brother.'—Jeremy Bush

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, estimated at six metres across and six metres deep, caused the home's concrete floor to cave in around 11 p.m. local time on 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 Bush's brother running.

Jeremy Bush said he jumped into the hole but couldn't see his brother and had to be rescued himself by a sheriff's deputy who reached out and pulled him to safety as the ground crumbled around him.

"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 neighbour's yard. "But I just couldn't do nothing."

He added: "I could swear I heard him hollering my name to help him."

A dresser and the TV set had vanished down the hole, along with most of Bush's bed.

Deputy Douglas Duvall, who was first on the scene, saw Jeremy Bush. Duvall said he reached down as if he was "sticking his hand into the floor" to help Jeremy Bush. Duvall said he didn't see anyone else in the hole.

As he pulled Bush out, "everything was sinking," Duvall said.

Engineers said they may have to demolish the small house, even though from the outside there appeared to be nothing wrong with the four-bedroom, concrete-wall structure, built in 1974.

Jeremy Bush said someone came out to the home a couple of months ago to check for sinkholes and other things, apparently for insurance purposes.

"He said there was nothing wrong with the house. Nothing. And a couple of months later, my brother dies. In a sinkhole," Bush said.