The number of registered voters in the 1st Congressional District has risen about 3 percent since the beginning of the year, the state Office of Elections said Thursday.

The office did not take an official count Thursday, the deadline for people in the district to register to vote in the mail-in only special election. Elections spokesman Rex Quidilla said because Thursday was only a postmark deadline, they'll wait until next week to do a final count.

Quidilla said he's not sure how much of the increase in registered voters can be attributed to interest in the congressional race.

The election was necessitated by the departure of Neil Abercrombie, who announced in December that he would resign to focus on a gubernatorial bid. He actually resigned at the end of February.

The major candidates are former U.S. Rep. Ed Case, Honolulu City Councilman Charles Djou, and state Senate President Colleen Hanabusa.

Elections staff said there were about 316,000 voters counted in the district earlier this week. There were about 307,000 at the beginning of the year.

The election is being conducted by mail. Registered voters will be mailed a packet with a vote-by-mail ballot and a return envelope. Packets will be mailed approximately 20 days before the election. Ballots must be returned in the envelopes provided by 6 p.m. on May 22.

Voters needing an accessible voting machine are eligible for walk-in voting at the Office of the City Clerk from May 10 to May 20.