BOSTON – Water to 2 million people in Boston and more than two dozen suburbs is unsuitable for drinking after a break in a pipe that connects a central Massachusetts reservoir to the area.

Repairs on the 10-foot-wide pipe in Weston began Saturday evening after state officials stopped the leak. Massachusetts Water Resources Authority head Fred Laskey says he hopes it can be fixed in “days, not weeks.”

The state issued a boil-water order for drinking water in the 30 affected communities, which include 2 million people in 700,000 households and Gov. Deval Patrick declared a state of emergency.

The break in a pipe in Weston, about 10 miles west of Boston, was leaking water into the nearby Charles River at a rate of 8 million gallons per hour, according to state officials. The Massachusetts Water Resources Authority was able to draw emergency water supplies from various reservoirs for bathing, flushing and fire protection. The state issued the boil-water order, however, because the water isn’t treated for drinking.

Authority Director Frederick Laskey called the break “unprecedented” and said it came at a critical area in the system.

“It’s highly unusual and catastrophic in nature,” he said.

The pipe carries water from the Quabbin Reservoir in central Massachusetts to the Boston area. The break was discovered at about 10 a.m. Saturday and continued to worsen until authorities were forced to shut down the water running through it.

Laskey said the pipe was “relatively new” — installed just six or seven years ago — and the state will be investigating why it failed.

He said it was impossible to know Saturday when the pipe might be repaired, and the boil-water order lifted, because the magnitude of the damage wasn’t clear.

“It’s a complex area of piping,” he said. “It’s a large pipe. It was probably custom-made. So it’s not as if there’s a yard we can go to and pick one up and just go and put it in. It’s a big problem.”

Area residents were notified about the order through reverse 911 calls and various media and public announcements. Boston Mayor Thomas Menino, who also declared a state of emergency in his city, said police had been to public housing projects to notify residents. Menino said city restaurants remained open for business.

“We don’t know how long this is going to last,” Menino said. “We want everyone working together.”

Dimitri Meletlidis, 48, the owner of Broadway House of Pizza in the suburb of Chelsea, said he learned about boil-water order on his cell phone and got messages in English and Spanish at his house.

He said he didn’t think the order would have a huge effect on his business.

“We don’t use a lot of water, because we make mainly pizza,” he said. “But we’re being very careful.”