Ford opened an internal probe in February after an anonymous employee reporting system first alerted the company to the issue in September 2018, according to the statement.
The federal criminal probe was first revealed Friday in filings with the US Securities and Exchange Commission.
“As previously reported, the Company has become aware of a potential concern involving its US emissions certification process. We voluntarily disclosed this matter to the US Environmental Protection Agency and the California Air Resources Board on February 18, 2019, and February 21, 2019, respectively.,” the filing reads.
“Subsequently, the US Department of Justice opened a criminal investigation into the matter,” the filing continues. “In addition, we have notified a number of other state and federal agencies. We are fully cooperating with all government agencies. Because this matter is still in the preliminary stages, we cannot predict the outcome, and we cannot provide assurance that it will not have a material adverse effect on us."
The issue of skirting emissions regulations has caused massive fines and investigations for several car manufacturing giants.
The EPA and Volkswagen agreed to a $14.7bn (£11.4bn) settlement over an emissions cheating scandal that found the company had installed “defeat devices” on its diesel engines.
The devices provide a capability for engines to detect when they are being tested, before switching to an alternative mode that reflects better emissions numbers.
Ford has previously stated its emissions issue is not related to defeat devices.
Fiat Chrysler was also alleged to have installed software on its Jeep and Ram vehicles to circumvent emissions rules, before signing an $800m (£619m) re-compensation agreement.
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