Federal safety regulators have upgraded a probe into 252,867 Mercedes-Benz C-Class cars for loss of rear lights that could cause a fire.

Vehicles released for the 2008-'11 model years are affected by the investigation, according to Edmunds.

The National Highway Traffic Safety Administration and Mercedes confirmed that over 402 complaints have been received involving the issue. Five of complaint alleged that the issue started a fire, according to the NHTSA.

"Consumers allege a loss of one or more rear lighting assemblies due to an overheated electrical connector that, in some cases, resulted in melting, smoke, or possibly a fire," said NHTSA in their summary of the problem.

An evaluation of the issue was opened this past July after 21 complaints of rear light assembly failure were received by the NHTSA.

Mercedes-Benz said regulators have received at least 291 complaints regarding the issue.

"Since opening the initial investigation, (NHTSA) has received a total of 114 complaints reflecting an ongoing and increasing trend," said the NHTSA. "In each report, one or both rear light assemblies fail completely when the electrical ground connection is compromised as a result of high resistance and subsequent thermal over-heating."

Mercedes-Benz has not commented about the investigation as of press time according to Edmunds.

The probe is now being called an "engineering analysis," which occasionally is followed by a recall.

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