Daniel Koh, a former chief of staff to Boston Mayor Martin Walsh, filed for a recount Friday in the Democratic primary for Massachusetts’ 3rd District, according to a media report.

“We want the process to progress as swiftly as possible so that the ultimate nominee will have adequate time and resources to win in November,” the Koh campaign said in a statement to the Boston Herald.

Front-runner Lori Trahan, a former aide to longtime 5th District Rep. Marty Meehan, declared victory in the 10-way primary Tuesday night, but with the race too close to call, Koh did not concede and all ballots for the race were sealed.

With the provisional ballot yet to be certified, official tallies for the race were not available Friday, said Debra O’Malley, a spokeswoman for the Massachusetts Secretary of State. The Associated Press reported Trahan led with 18,368 votes, narrowly edging out Koh’s 18,316. The third-place finisher, Lawrence state Rep. Juana Matias, netted 12,914 votes.

Representatives from Koh’s and Trahan’s campaigns did not return requests for comment Friday. 

The race, a rare open seat in Massachusetts’ all-Democrat delegation, was hotly contested, with 10 candidates from throughout the state, many of whom had experience with and backing from prominent national groups and political figures. 

Massachusetts has an all-paper ballot, so each municipality will have to hand-count its ballots, making it difficult to determine when the results will be known, O’Malley said. 

The winner will replace longtime Rep. Niki Tsongas, who is retiring after five terms.