In a 104-to-92 vote, newsroom employees at the Contra Costa Times, Oakland Tribune and other East Bay newspapers controlled by MediaNews have voted for representation by the Northern California Media Workers Guild. About 90 percent of the participating staff cast ballots, according to the Chronicle, which said the union spent more than 18 months and $500,000 on a campaign to strengthen its hand at MediaNews.

The Chron said management declined to be interviewed, but issued a written statement: “We feel a union-free environment is best for our employees,” said John Armstrong, president and publisher of Bay Area News Group-East Bay, the company that operates the newspapers. “This has been an emotional experience for everyone involved.” But he said he and other newspaper executives were committed to “moving in a positive direction” with staff.

The Chronicle story contained an unusual disclosure statement at the end: “Full disclosure: Reporter James Temple worked at the Contra Costa Times during and after the MediaNews purchase. Another Chronicle reporter, Carl Hall, went on leave to oversee the organizing drive.”

CORRECTION: We originally reported that only 53 percent of participating staff members cast ballots in the election. That was based on the Chroncle’s report. Sara Steffens, a leader of the union movement, tells us the actual percentage was nearly 90 percent — 196 votes out of a unit of 225 people. The item above has been corrected.