German auto giant Volkswagen said Thursday that an independent probe it has commissioned into the global pollution-cheating scam is likely to take "several months".

VW, which has admitted to fitting sophisticated software in its diesel engines to skew emission testing, has commissioned US legal firm Jones Day to conduct an independent investigation into the affair that has rocked the entire automobile sector. 

Key members of the automaker's supervisory "are of the opinion that the investigations will take several months before they can be completed," the company said in a statement.