Matthias Mueller, the newly-appointed CEO of embattled carmaker Volkswagen, said late Monday that the company has a “comprehensive” plan to refit cars equipped with “defeat devices” that helped them cheat U.S. diesel emissions tests. The European Commission also announced it would review its approval system in light of the scandal.

The use of the software, which was revealed earlier this month, led to the eventual resignation of Volkswagen’s former chief Martin Winterkorn, pummeled the company’s stocks, and triggered widespread investigations into the carmaker’s practices. With German authorities announcing a criminal investigation of Winterkorn on suspicion of fraud, the company is under huge pressure to tackle the biggest business-related crisis in its 78-year history.

“We are facing a long trudge and a lot of hard work,” Mueller reportedly said. “We will only be able to make progress in steps and there will be setbacks.”

According to the plan, Volkswagen will ask customers “in the next few days” to have their diesel vehicles refitted, Reuters reported, citing Mueller's comments during a meeting of the automaker's top managers at its Wolfsburg headquarters.

On Tuesday, the European Commission also announced that it would work toward reforming its current system of approving new models of cars -- the so-called type-approval system that currently leaves member states in charge of ensuring compliance to Europe's emission rules.

“The focus is on clarifying and strengthening the recall system and the exchange of information among type approval authorities,” an unnamed spokeswoman for the Commission told Reuters, adding that the new rules -- to be outlined by the end of this year -- would “streamline the procedures for co-operation and information exchange between the member states.”

Last week, Volkswagen revealed that as many as 11 million vehicles -- including 5 million of its namesake brand, and over 3 million at subsidiaries Audi and Skoda -- carry the emissions-rigging software. At the time, Volkswagen also cut its earnings outlook as it set aside 6.5 billion euros ($7.3 billion) to cover costs related to the scandal.