A glitch by phone operator SFR meant that text and voice messages to the unemployed asking them to update their status were never delivered, causing the number registered as jobless dropped by 50,000 in August, according to France's unemployment office.
In a statement late Monday the office said it was investigating.
The drop reported Sept. 25 would have been the biggest in 13 years.
Nevertheless, the actual number was still a decline of between 22,000 and 29,000 — after 27 straight months of increases.
"We have to have reliable figures," Laurent Berger, head of the CFDT union, told France Info radio Tuesday.
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