The rise in participation was consistent with turnout figures at noon, at which time 19.26 percent of voters had cast ballots, compared with 15.70 percent in 2014.
Forty-seven million voters registered in France have the right to elect 74 members to five-year terms in the European Parliament. The number of seats would rise to 79 when Britain leaves the bloc.
The 5pm announcement meant turnout in France was already higher than the final participation rate of 43 percent in 2014.
Two polling institutes estimated final turnout in metropolitan France (not counting overseas departments and territories) would be between 52 and 54 percent.
Ifop-Fiducial estimated 54 percent, while Harris-Interactive/Epoka estimated 52.2 percent.
Early results of the election were to be announced at 8pm local time, with official results expected later in the evening.