Volkswagen announced that next January it will begin recalling 8.5 million diesel vehicles in Europe, with repairs to bring the cars back into emission compliance after it was discovered they are over-polluting.

The decision came after Germany’s Federal Motor Transport Authority (KBA) ordered the company to recall 2.4 million vehicles. According to Arndt Ellinghorst, senior managing director and head of the global automotive research for analysis firm Evercore ISI, firm recall orders are not standard protocol for Germany.

“It’s an unusual measure to be ordering a mandatory recall,” Ellinghorst said. “It shows to me that the KBA is losing patience with VW’s slow response on what to do to fix the engines so far. Customers have been left unsettled.”

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The KBA has also established deadlines for Volkswagen’s recall: technical details on the repairs must be submitted for review by mid-November, and the recall must begin in January.

This truncated schedule buys VW engineers a little more time to come up with a solution for the affected 2.0-liter engines to meet emission regulations. Last month, KBA Minister Alexander Dobrindt notified Volkswagen that the company had until October 7 to present its resolution. Volkswagen, which has not yet identified a fix, proposed a voluntary recall. This was rejected by German officials.

Volkswagen stated that it supports the KBA’s “swift decision” for the mandatory recall. As reported by Bloomberg, newly-appointed CEO of Volkswagen Group Matthias Müller responded directly to Dobrindt in a letter.

“The KBA’s decision opens up the possibility of a common and coordinated response in all European Union states,” wrote Müller. “Such a unified procedure would be in the European spirit as well as in the interests of customers.”

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Volkswagen has two main options to reduce emissions on these diesels: a software update, or added hardware. Both are likely to be costly repairs. Volkswagen hasn’t yet specified a solution, but did state that engineers were working quickly to develop one.

“Work on the technical solutions … is currently proceeding at full speed,” Volkswagen said. “These are currently being developed for each affected series and each affected model year. All measures will first be presented to the responsible authorities. Volkswagen will subsequently inform the owners of these vehicles over the next weeks and months.”

In the U.S., the Environmental Protection Agency is holding back on issuing a recall for now. The department said it is waiting to see first what Volkswagen solution will be, and wants to verify that the solution is effective before a U.S. recall will begin.

“EPA will order a recall in the future, but will not do so until we are confident that VW’s fix will work,” said EPA representative Laura Allen. “EPA will conduct our own testing to confirm this. Then we will order a recall.”