Votes against a measure to add fluoride to Bellingham’s drinking water continued to grow Monday, reaching a 244-vote lead.

Unofficial election results released by the Whatcom County Auditor’s Office show 50.9 percent of voters rejecting the measure and 49 percent supporting it.

Election workers have counted more than 37,000 ballots since the Nov. 8 general election. Officials estimate 25,000 ballots are left to count.

The first ballot counts showed a slight majority supporting adding fluoride to the drinking water of more than 86,000 people in and around the city of Bellingham. The measure’s lead dropped to only a 68-vote margin Thursday. By Sunday, the ballot count had the measure losing by 91 votes.

Now, with a 244-vote margin going against the measure, fluoride opponents including Rainy Fackler-Adams are happy but still guarded as election results continue to come in.

“I think it’s amazing you can come in here with more than $250,000 worth of advertising … and people can still think for themselves,” said Fackler-Adams, who unsuccessfully sued to keep the measure off the ballot. “I’m proud of Bellingham, but it may be too soon to talk.”

Bellingham Families for Fluoride, the political action group supporting the measure, spent more than $260,000 in its campaign, more than any other issue in city history. Fluoride opponents created a series of grass-roots groups to speak out against the measure.

Curt Smith, a retired Bellingham dentist who co-chaired Bellingham Families for Fluoride, agreed it was too soon to say how the vote will turn out.

“We have to wait until we have three-quarters of the ballots counted to get a clear picture,” Smith said. “We would prefer to be ahead, but it is what it is.”