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The battle between the Bernie Sanders campaign and the Democratic National Committee over the use of the D.N.C.’s voter data officially ended Friday, with the campaign withdrawing its lawsuit against the party.

The fight between the committee and the Vermont senator’s campaign began in December when several members of Mr. Sanders’s data operation were found to have gained access to, searched and stored proprietary information from Hillary Clinton’s team because of a software glitch with the voter database. The party quickly denied the Sanders campaign future access to its 50-state voter file, which contains information about millions of Democrats and holds daily value for campaigns.

In response, the Sanders campaign sued the D.N.C. and accused it of actively trying to help Mrs. Clinton. Eventually, the party and the Sanders campaign agreed to restore access to the voter file while the party continued to investigate the breach.

On Friday, the committee said the investigation had found that four Sanders staffers gained access to the database for an hour and did 25 searches using proprietary Clinton data from 11 states. The statement said all of the search results were saved in a computer system except in one instance, when a Sanders staffer exported information using Clinton data for New Hampshire.

In statement released Friday, the Sanders campaign said that an investigation of their computers could not locate the exported file, and that no one in the Sanders campaign had ever seen it. The campaign said that it had fired the staffers involved, and that no one else in the campaign “accessed the Hillary for America’s scoring models or had knowledge that the activity was taking place until well after the incident was over.”

The D.N.C. investigation also found that Clinton staffers and workers for Martin O’Malley, one of the early candidates for the nomination, did not access any of their rivals’ data.