"The nuclear power plant in Leibstadt informed the Federal Nuclear Safety Inspectorate (IFSN) a few days ago that some of its fuel production components did not meet specifications", the agency said in a statement.
Areva said the problem was linked to the "sporadic dysfunction of the control system" in zirconium tubes, which are used to encase fuel rods at nuclear plants.
The company said the issue occurred at its Paimboeuf production site in Western France.
Areva said it had informed its customers that the tubes should not be used.
The IFSN said that the Leibstadt plant had already been shut down for regularly scheduled maintainance when the problem emerged, and that the site would remain closed through the end of the year while the issue was resolved.
The tubes are being replaced "for safety reasons", the agency said.
A statement from the plant said that six tubes were deemed defective, representing less than one percent of the material in use at the site, and that "no damage" had been recorded.
"No system containing the tubes concerned demonstrated even the slightest failure so far", Areva said.
The safety of nuclear energy has been a contentious political issue in Switzerland for years.
In a May referendum, voters backed an overhaul of the country's energy system by gradually replacing nuclear power with renewable sources.