The strike occurred at midnight Monday after union negotiations with the developer and construction general contractor, Perini Building, over the construction site's safety broke down.

The walkout came on the heels of Saturday’s death of a sixth worker at the construction site in the last 16 months. Dustin Tarter, a 39-year-old worker from Henderson, Nev., was killed Saturday when he was working on a moving crane and apparently became caught between the counterweight system and the track of the crane.

The Southern Nevada Building and Construction Trades Council called for Perini to pay for additional safety training; authorize the union to research the cause of the safety problems; and give union leaders full access to the CityCenter job site. Perini officials had reportedly agreed to the demands informally but hadn’t officially followed through until Tuesday afternoon. After Perini agreed to the demands Tuesday afternoon, union workers returned to their jobs that night.

CityCenter, slated to open in late 2009, includes a 4,000-room hotel-casino, high-end condominiums, boutique hotels and a retail, dining and entertainment complex.

Dubai World, the investment arm of the Persian Gulf state of Dubai, owns 50 percent of CityCenter.

—Staff reports