Washington's health care exchange shut down after the first few hours of open enrollment Saturday as state officials and software engineers tried to resolve a problem with tax credit calculations.

Officials at the exchange said Washington Healthplanfinder, which opened at 8 a.m., appeared to be working fine at first. When the exchange's quality control system reported the problem, they decided to shut the whole system down at about 10:30 a.m. to fix it.

The tax credits were off by just a few dollars in some cases, exchange CEO Richard Onizuka said. He said the system would remain down until it can give consumers who want to buy health insurance accurate information.

On Saturday afternoon, officials estimated the site wouldn't reopen until Sunday morning, but the actual timing will depend on how soon a software fix can be tested for potential side-effects.

Exchange officials could not say how many people had signed up for insurance before the problem was discovered, but spokesman Michael Marchand said about 2,000 people were using the exchange each hour during the two hours it was open on Saturday morning.

Officials decided to shut down the exchange -- which was working well otherwise -- instead of fixing the problem later because they learned after the previous open enrollment period that even small issues are difficult to fix after registrations are complete, Marchand said.

"It's really bittersweet," Marchand said. "The site worked so much better than last year."

It was also disappointing because the quality control group did such a good job catching the problem just by looking at numbers on a spreadsheet, he added.

"It's a feat that would make auditors jealous," Marchand said.

Katie O'Brien, 21, who stopped by a signup event for the Washington exchange on her way to work at Southcenter Mall in Tukwila, Washington, said she was happy to pick up some information since she has a health condition that requires medication and she recently lost her insurance when she quit working at Starbucks.

O'Brien said she didn't have time to sign up on Saturday, because she was almost late for work at Hot Topic, so she wasn't concerned that the exchange website was down.

O'Brien, who makes less than $400 a month, said she was happy to learn that she may be eligible for nearly free insurance.

"I'm actually pretty uneducated about it," she said of insurance available through the exchange.

Open enrollment for health care insurance continues through Feb. 15, and officials are hoping as many as 85,000 people sign up in Washington state this season. They also hope all of the about 145,000 people who bought insurance during the first open enrollment period, which began Oct. 1, 2013, will renew for another year.

Those who run the exchange had been hoping their computer system would handle traffic better than it did last year, when it shutting down and rejected applications for reasons like a hyphen in a last name. About a thousand people who bought insurance the first time around are still having problems getting their payments credited and that money transferred to their insurance companies.

Gregory Boxly, 62, who has been paying more than $500 a month for insurance since he retired, said the Healthplanfinder event at Southcenter Mall reminded him he needed to do more research to find out if he could get cheaper insurance through the exchange.

He said he was concerned that insurance through the exchange may not pay for dental or vision care, but he'll check out the choices when the website is working again. He wasn't concerned about waiting to log on.

"I worked in IT," he said with a smile, adding that computer problems are inevitable.

People who do not buy insurance will have to pay a fine when they file their income taxes. Those fines start at $95 or 1 percent of 2014 household income, but the minimum fine in 2015 will be $325 per uninsured person or 2 percent of household income.

Consumers will find more choices this time around, with more insurance plans and more companies on the state's exchange. Rates have gone up slightly overall but some people will find cheaper insurance.