Nearly 660,000 vote-by-mail ballots have been cast in the Aug. 23 primary elections, with in-person early voting starting soon, according to data posted on the state Division of Elections website.

Of the 659,589 vote-by-mail ballots returned as of Thursday morning, 290,846 had come from registered Democrats and 257,885 from registered Republicans.

Another 8,301 had been returned by people registered with third parties, and 102,557 were cast by people without party affiliation.

About 3.4 million additional vote-by-mail ballots had been distributed but not returned.

Of that amount, 1.5 million had been distributed to Democrats and 1.06 million had gone out to Republicans.

In-person early voting is required to be offered from Aug. 13 to Aug. 20, while a number of counties will open early-voting sites on Monday.