Ameristar Casino had an unlucky construction blast that shut down the Black Hawk gaming parlor for the day.

The 7 a.m. "controlled blast" to clear a hillside behind the casino for a new hotel unleashed too big a rock slide and a wall of rock that knocked down masonry wall for a mechanic room, said Ameristar spokeswoman Heather Leigh. It also burst a pipe, causing water damage.

To ensure safety, the explosion was conducted before the casino opened. Hundreds of workers were sent home for the day.

"We're happy to tell you no one was injured," she said. "Our goal is to reopen Saturday."

The casino has been conducting control blasts for the past two months to clear a footprint for a new 33-story luxury hotel with 536 rooms. The hotel is scheduled to open in mid-2009.