Crews with heavy equipment have begun the demolition of a Florida home over a huge sinkhole where a man is presumed dead after being swallowed by the earth.

The search for Jeff Bush, 37, was called off Saturday, and a heavy machine with a large bucket scoop was moved into position Sunday.

The 20-foot-wide opening of the sinkhole was almost covered by the house, and rescuers said there were no signs of life since the hole opened Thursday.

 Jeremy Bush, the man who tried to save his brother, was escorted with a woman by a deputy to the front of the house early Sunday before equipment moved into position.

He repositioned some flowers from a makeshift memorial to a safer location, where Bush and the unidentified women knelt in prayer.

Bush, 37, was in his bedroom Thursday night in Seffner — a suburb of 8,000 people 15 miles 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 organized 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 Friday, was allowed to go inside for about a half-hour to gathering belongings.

Sisters Soliris and Elbairis Gonzalez, who live on the same street as Bushes, said rumors were circulating among neighbors, 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, 35 miles away from Seffner. The Largo sinkhole, at about 10 feet 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.

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 Saturday what, if anything, caused the Seffner sinkhole.

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

Engineers had been testing in the area of the Bush house since 7 a.m. Saturday. By 10 a.m., 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.

Jeremy Bush, who tried to rescue his brother, lay flowers and a stuffed lamb near the house 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," Bush said Friday.

The sinkhole, estimated at 20 feet across and 20 feet deep, 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.