After working around the clock for two days, crews bolted new pipes into place Saturday evening to repair a broken water line that had spewed 14 million gallons onto downtown Minneapolis streets.

City officials estimate that water should be restored to the area by noon Monday.

Before water resumes, the new pipe -- 3 feet in diameter and 13 feet long -- must be examined for leaks, disinfected with chlorine, and flushed to remove the chemicals. Then the water will be tested to ensure its safety. The chlorination process takes about nine hours and the testing another 24 hours.

Testing will be done by the city's water quality lab with observation by the Minnesota Department of Health, said Marie Asgian, the city's superintendent of water distribution. The two agencies are cooperating "to be sure that the water quality is 100 percent," she said.

The water main broke about 2:30 p.m. Thursday on N. 2nd Street at Hennepin Avenue at the construction site for a $70 million retail-apartment complex that will include a Whole Foods Market. The break occurred when a subcontractor for Ryan Companies, which is building the complex, was boring under the street to install a sleeve for a sewer line linking the new building to the city's sewer system.

Repair crews lifted out a 12-foot length of broken pipe Saturday. "The whole length of pipe was split from end to end and there was also about a 2 1/2-feet-by-7-feet-long piece blown out. It was really huge," said Mark Ebert, Minneapolis' general foreman for water distribution, who had been supervising repair work. "I've been with the city 33 years and this is the largest water-main break that I've known," he added.

Asked what caused the blow out, Ebert declined to speculate. But, he added, "We've definitely found the smoking gun."

He referred further questions to a water department spokesperson who could not be reached Saturday.

Scott Beron, safety director for Ryan companies, said experts would be called in to determine the cause of the break. "There are different scenarios. Did they hit it? Was the main weakened and the work caused it to come loose? Nobody knows. It's kind of a mystery now," Beron said.

The cost of the damage is still undetermined. Insurers are expected to pay some of it, and the city plans to seek reimbursement for its clean-up and repair from the party that caused the damage.

Businesses in the area were forced to close early on Thursday when water was shut off, and some customers avoided the area over the weekend. Parts of a nearby parking garage at the main downtown post office were flooded and an estimated 50 vehicles belonging to employees or the Postal Service were submerged.

Mary Abbe • 612-673-4431