BERLIN (AP) — German news agency dpa is reporting that several of the country's automakers are going to recall a total of 630,000 cars following an investigation into emissions levels.

Citing unidentified government sources, dpa reported Friday that the manufacturers would need to change technology used to switch off the vehicles' emissions treatment systems at certain temperatures.

Public broadcaster ARD reported that the recall was voluntary.

German auto giant Volkswagen has already acknowledged using special software to cheat on U.S. diesel emissions tests and offered to pay substantial fines and compensation to American owners.

The Federal Transport Ministry declined to comment on the reports but said its top official will hold a news conference at 3 p.m. (1300 GMT).