Investigators are trying to determine why a crane collapsed at the site of a South Florida residential construction project, killing a construction worker and damaging a neighboring house. Christopher J. Ricci, 27, of Sunrise, Fla., was struck by the crane's boom and died instantly in the June 12 accident, a police spokeswoman says.

DLS Prestressed Inc., Pompano Beach, Fla., was using the lattice-boom truck crane, which was riding on rubber tires, to install piling for construction of a two-story, single-family home in a residential neighborhood in Hallandale Beach, Fla. It was being moved on the site with the boom raised and carrying a drill-rig attachment.

"As the crane was moving, it started to wobble a little bit—unsteady," Hallandale Beach Police Captain Sonia Quinones told local news media. "At that point, it started to topple over. Construction workers noticed what was taking place, and they took off running. Unfortunately, one of those construction workers was struck by the boom and killed instantly."

A house on the site was demolished in 2011, and a seawall was repaired afterward. Work has proceeded fitfully for the past six months or so, and the site has been staked a couple of times, says Geoffrey Siegel, a neighbor. The crane arrived on the site on June 9. On the night before the accident, heavy rain fell intermittently in "squalls," Siegel says, and he speculates the ground may have been soft on the site.

Quinones and spokespersons for the Occupational Safety & Health Administration declined to comment, citing the ongoing investigation.

The permit for the site was issued to Certified Building Systems Inc., Coral Springs, Fla., in the name of Vincent Enea, president, for a two-story, single-family home valued at $850,000. Certified Building is the general contractor, and DLS Prestressed is listed as a subcontractor. Neither company responded to calls for comment.

The site, surrounded entirely by water, is located on an artificial island at the edge of a canal—a common configuration in South Florida. Such developments usually are built on former mangrove forest land infilled with soft organic material, says a geotechnical engineer, who requested anonymity to avoid being mentioned in a story that might result in a lawsuit. "Residential homes quite commonly are built" on foundations of tangent auger-cast walls on such lots, he says.

An expert on crane accidents, who also requested anonymity for this story, says moving a crane carrying a swinging load is a risky endeavor.

"If it's a lattice-boom truck crane on rubber tires with no outriggers, you're playing with fire," the expert notes.