Voters in Washington state have approved gay marriage.

The Associated Press called the race on Thursday, minutes after opponents of Referendum 74 conceded, saying the ongoing return of late election results has shown they haven't closed the gap.

Preserve Marriage Washington issued a statement saying that while they're disappointed with the results, they will "continue to educate citizens and policymakers on the timeless truth that real marriage is the union of one man and one woman."

Gay couples could in Washington start picking up their marriage certificates and licenses from county auditor offices Dec. 6, a day after the election is certified. However, because Washington has a three-day waiting period, the earliest a certificate could be signed, making the marriage valid, is Dec. 9. 

On Wednesday, supporters of gay marriage declared victory on Referendum 74, which asked people to approve or reject a law legalizing same-sex marriage that state lawmakers passed earlier this year. That measure was signed by Gov. Chris Gregoire, but it was on hold pending the outcome of Tuesday's election and has never taken effect..

Many supporters started celebrating early, taking to the streets in a Seattle neighborhood and cheering at election watch parties Tuesday night as early result showed the referendum taking a narrow lead. Police closed off several blocks in Seattle's Capitol Hill area as more than 1,000 people gathered for a late-night, impromptu election celebration, dancing and chanting "74, 74, 74."  

Washington is one of four states where voters were asked about the issue this election cycle. Maryland and Maine approved gay marriage Tuesday night, while Minnesota voters rejected a proposed constitutional amendment to ban it.     

The District of Columbia and six states -- New York, Connecticut, Iowa, Massachusetts, New Hampshire and Vermont -- already allow gay marriage. But their laws were enacted either by lawmakers or court rulings.