OLYMPIA, Wash. (AP) — Vermont Sen. Bernie Sanders and former Vice President Joe Biden were virtually tied in early statewide returns in Washington’s vote-by-mail presidential primary Tuesday night, but it will take days to receive and tally all the votes.

With most counties posting their first batch of results, Sanders led by about 2,000 votes. Counties will update their results again Wednesday afternoon.

As of Tuesday night, turnout was near 40%, with more than 1.8 million voters having returned their ballots, and just over a million votes were counted. The numbers don't reflect ballots dropped in drop boxes Tuesday or those which may still be in the mail. The majority received thus far— nearly 1.2 million — are Democratic ballots.

Of the state’s 89 pledged delegates, only 31 are allocated based on the statewide result. The remaining 58 are determined based on the results of the state’s 10 congressional districts, and those results might not be calculated until the election is certified by the secretary of state’s office, which could be as late as March 27.

Of the six states voting Tuesday, Washington offers the second-highest number of delegates to be divvied up, behind Michigan's 125.

Democrats are using the vote-by-mail presidential primary — moved up this year from May — for the first time to allocate delegates instead of the smaller caucuses used in previous years.

The Washington ballot had 13 candidates on it, along with an ‘uncommitted’ option. But it's essentially a two-person race between former Vice President Joe Biden and Vermont Sen. Bernie Sanders. President Donald Trump is the only candidate listed for Republicans.

Gagan Thind, 39, dropped her ballot off at a drop box in Seattle Tuesday, saying that she and her husband both voted for Biden “because we wanted the best chance to win against Donald Trump.”

Seattle voter Jillian Kessell, 22, said she voted for Sanders because “Elizabeth Warren wasn’t in the race anymore.”

In 2016, Sanders won more than two-thirds of the delegates from the Washington caucuses that year, which were attended by about 230,000 Democrats. More than 800,000 Democrats sent in ballots for the primary later that year — which Hillary Clinton won — even though their vote didn't count for the nominating process.

The state Democratic Party's central committee voted last year to start using a hybrid system that uses the state’s vote-by-mail system for a presidential primary to apportion delegates to candidates, and caucuses and conventions to select which delegates will represent the state at the national convention in Milwaukee in July. Also last year, Washington Gov. Jay Inslee signed a measure moving the state's presidential primary from May to the second Tuesday in March.

Both parties have rules that only voters who identify with a party may participate in the primary to allocate delegates to the national nominating conventions. Washington state has no party registration, and in order to have their vote in the presidential primary counted, voters must sign a pledge on the envelope affirming to being either Republican or Democrat. They can only vote in the race that corresponds with their party. As of Tuesday night, more than 65,000 ballots were at risk of being invalidated because a party was not chosen, or in the case of 781 voters, they chose both parties. Elections officials will contact each of those voters to see if they want to select a party in order to have their vote count.

Will Casey, a spokesman for the state Democrats, said that under Democratic National Committee Rules, if any listed candidate hits the 15 percent threshold in voting, they are allotted delegates, even if no longer in the race. Those delegates will be pledged to that candidate on the first ballot, though they can ultimately be released by that candidate.

In order for the uncommitted category to have delegates, it also must hit that same threshold. As of Tuesday night, no one other than Biden and Sanders surpassed that threshold.

On Monday, Deanna Knudsen of Snoqualmie said she had already cast her vote for Warren although others had tried to sway her into waiting in case Warren dropped out.

“My belief is the primary is the time to vote your heart, and the general is the time to vote with your head and be pragmatic,” she said, adding that she will back the Democratic nominee no matter who it is.

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AP writer Lisa Baumann and AP photo stringer John Froschauer contributed to this report from Seattle.