premeditated commission: No sign of Fla. man swallowed by sinkhole

Hillsborough County, Florida officials lay out their plan going forward at the site of a sinkhole that appeared beneath a home and is believed to have killed one of the residents.

By Ian Johnston and Matthew DeLuca, NBC News

Rescue workers on Saturday called off their search for a 36-year-old Florida man swallowed by a sinkhole that appeared under his bedroom, an official said, after engineers spent the day testing the unstable ground around the chasm.

Jeffrey Bush had not been heard from since the hole appeared at about 11 p.m. ET Thursday in Seffner, near Tampa.

?Unfortunately we have not been able to determine the whereabouts of Mr. Bush,? Hillsborough County Administrator Mike Merrill said. ?With all the equipment that we brought in and specialized help, we have just not been able to locate Mr. Bush, and so for that reason the rescue effort is being discontinued.?

Authorities have said the hole, which was originally about 30 feet deep, was ?seriously unstable.? A 100-foot safety zone was set up around it Friday and homes near the hole were evacuated for fear of a sudden collapse.

The sinkhole now poses a safety risk to the residence next door, said Hillsborough County Fire Rescue public information officer Ronnie Rivera at a noon press conference on Saturday. Family members would be allowed to enter briefly along with emergency personnel to recover belongings, Rivera said.?

A second family in an adjacent home began moving their possessions out on Saturday afternoon as authorities struggled to get an accurate read on just how large the sinkhole is.

Authorities will begin bringing in heavy equipment to demolish the home from outside the perimeter of the sinkhole, which Merrill said extends down as much as 50 to 60 feet.

?We?re dealing with a very unusual sinkhole,? Merrill said. ?It?s very deep, it?s very wide, it?s very unstable.?

Merrill said workers would move from rescue to demolition operations.

?Any further demolition can?t even take place on the site,? Merrill said. ?It needs to be done from outside the perimeter with huge equipment that will be able to reach in and bring out whatever we can of the house.?

On Friday, Jeremy Bush spoke tearfully about how he tried to save his brother.

"I couldn't get him out," he said. "All I thought I could hear was him screaming for me and hollering for me, but I couldn't do nothing."

Jeremy Bush was saved from the hole by Hillsborough County sheriff's Deputy Douglas Duvall, NBC station WFLA reported.

'Really shocking'
Neighbors told NBC station WFLA.com of their surprise.

"It's just really shocking," said Kevin Charles, who lives two houses down from the Bush?s house. "It kind of worries me because ? it could have been any one of these houses along this side over here.?

"I think the issue now is everyone in the area is going to sit back and wonder whether should get sinkhole insurance," said neighbor Steve Hamlyn. "Because we really didn't see a need for it until now."

While some in the neighborhood did not know of the risks, sinkholes are common in Florida, The Associated Press reported, and home insurers are required by law to provide coverage for the sudden disaster.

Florida?s geological makeup increases the likelihood of sinkholes, and more than 500 have been reported in Hillsborough County since 1954, the state?s environmental agency told the AP. A monster 400-foot sinkhole that sucked in a house, five sports cars, two businesses and part of a swimming pool appeared near Orlando in 1981.

"You can almost envision a piece of Swiss cheese," Taylor Yarkosky, a sinkhole expert from Brooksville, Fla, told the AP. "Any house in Florida could be in that same situation."

At a press conference at 8 a.m. ET Saturday, fire officials announced they had set up an email address, accessible at www.firefighter-relief.com, for anyone wishing to send message of condolences or donations to the family.

NBC News' Gabe Gutierrez and The Associated Press contributed to this report.