SEFFNER, Florida (AP) - The effort to find the body of a Florida man who was swallowed by sinkhole under his Florida home was called off on Saturday while crews tried to learn how far the underground cavity reaches and whether more homes are at risk.

Hillsborough County Administrator Mike Merrill said rescuers were ending the effort to find Jeff Bush's body and they planned to bring in heavy equipment on Sunday to begin demolishing the four-bedroom home.

"At this point it's really not possible to recover the body," Mr Merrill said, later adding "we're dealing with a very unusual sinkhole." Mr Bush, 37, was in his bedroom on Thursday night in Seffner - a suburb of 8,000 people east of downtown Tampa - when the earth opened and took him and everything else in his room. Five others in the house escape unharmed.

On Saturday, the normally quiet neighborhood of concrete block homes painted in Florida pastels was jammed with cars as engineers, reporters, and curious onlookers came to the scene.

At the home next door to the Bushes, a family cried and organised boxes. Testing determined that their house also was compromised by the sinkhole, according to Hillsborough County Fire Rescue spokesman Ronnie Rivera. The family, which had evacuated on Friday, was allowed to go inside for about a half-hour to gather belongings.

Sisters Soliris and Elbairis Gonzalez, who live on the same street as Bushes, said rumours were circulating among neighbours, with people concerned for their safety.

"I've had nightmares," Soliris Gonzalez, 31, said. "In my dreams, I keep checking for cracks in the house." They said the family has discussed where to go if forced to evacuate, and they've taken their important documents to a storage unit.

"The rest of it, this is material stuff, as long as our family is fine," Soliris Gonzalez said.

"You never know underneath the ground what's happening," added Elbairis Gonzalez, 30.

Experts say thousands of sinkholes erupt yearly in Florida because of the state's unique geography, though most are small and deaths rarely occur.

"There's hardly a place in Florida that's immune to sinkholes," said Sandy Nettles, who owns a geology consulting company in the Tampa area. "There's no way of ever predicting where a sinkhole is going to occur."

Most sinkholes are small, like one found Saturday morning in Largo, 56km away from Seffner. The Largo sinkhole, at about 3 metres long and several feet wide, is in a mall parking lot. Such discoveries are common throughout the year in Florida.

The state is prone because it sits on limestone, a porous rock that easily dissolves in water, with a layer of clay on top. The clay is thicker in some locations - including the area where Bush became a victim - making them even more prone to sinkholes.

Mr Jonathan Arthur, the state geologist and director of the Florida Geological Survey, said other states sit atop limestone in a similar way, but Florida has additional factors - extreme weather, development, aquifer pumping and construction - that can cause sinkholes. "The conditions under which a sinkhole will form can be very rapid, or they can form slowly over time," he said.

But it remained unclear on Saturday what, if anything, caused the Seffner sinkhole.

"The condition that caused that sinkhole could have started a million years ago," Mr Nettles said.

Engineers had been testing in the area of the Bush house since 7am local time on Saturday. By 10am, officials moved media crews farther away so experts could test a home across the street.

Experts spent the previous day on the property, taking soil samples and running tests - while acknowledging that the entire lot where Bush lay entombed was dangerous. On Saturday, officials were still not allowing anyone in the Bush home.

Mr Jeremy Bush, who tried to rescue his brother, laid flowers and a stuffed lamb near the house on Saturday morning and wept.

He said someone came to his home a couple of months ago to check for sinkholes and other issues, apparently for insurance purposes, but found nothing wrong.

State law requires home insurers to provide coverage against sinkholes.

"And a couple of months later, my brother dies. In a sinkhole," Mr Bush said Friday.

The sinkhole, estimated at 6 metres across and 6 metres deep, caused the home's concrete floor to cave in around 11pm 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.