The concrete is being piped into the dirt to firm it up and provide a stout base for the building. Officials estimate the $9-million, class-A asset, owned by Southpoint Investments, will be closed for at least a week.

The act of nature occurred in one of the hottest commercial real estate development markets in Central Florida, eight miles north of Downtown Orlando.

"It's going to take about 100 trucks" of poured concrete to firm up the loose limestone and sand that triggered the sinkholes, a representative of the city manager's office tells GlobeSt.com. "Nobody is going back into that building until we are absolutely satisfied there are no structural defects."

The evacuation of 400 office workers was ordered after the sidewalk buckled, a tree fell down and an exterior wall at the building started sagging Monday. The structure itself was not seriously damaged.

Construction industry estimators tell GlobeSt.com the preliminary damage estimate is at least $100,000.

Dry weather conditions loosened the limestone and sand but did not cause a large cavity directly under the building as most sinkholes do, city engineers tell GlobeSt.com. Instead, the engineers found about 75 feet of dry, porous soil that is causing the building's exterior walls, trees, sidewalks and outside doors to list.

Sprint Communications Co., the building's largest employer, moved 285 technical and sales personnel to other Sprint-leased buildings in metro Orlando. The company's production was not hindered by the evacuation, a Sprint corporate affairs representative tells GlobeSt.com.

In addition, the sinkholes have not affected the operation of nearby apartment complexes, office and commercial buildings such as the 280,000-sf Praedium IV Maitland Forum, the 350,000-sf RDV Sports Complex owned by Orlando Magic basketball baron Rich DeVos and the 700-room Sheraton Hotel.

The largest recorded sinkhole mishap in Central Florida annals occurred in 1981. A 350 foot-wide hole swallowed a car dealership showroom, a residence and a city-owned swimming pool in Winter Park, FL, not far from the current Maitland accident. Left standing and intact was a 2,000-sf dry cleaning shop next door.

Maitland Center, where Southpoint Building is located, is a conglomeration of 49 individually-owned office structures housing about 8,000 workers and comprising 5.25 million sf in properties valued at an estimated $20 billion, according to the Orange County Property Appraiser's Office.

The area has been known as a sinkhole hotbed since 1981 when the first office building was erected.

"Why do developers and investors then pour money into a vehicle that could completely evaporate in hours by an act of nature?" Dean Fritchen, a senior broker at Arvida Realty Services Commercial Division in Winter Park, asks GlobeSt.com. "Because of the excellent location to Interstate 4 and because most developers and investors have a bit of a gambling streak to them as well," he answers.