FRANKFURT (Reuters) - German public prosecutors have started investigating Daimler Chief Executive Dieter Zetsche on suspicions of involuntary manslaughter involving the fatal accident of a 27-year-old engineer caused by an intern on a test track.

"There is an investigation," senior public prosecutor Alexander Retemeyer told Reuters on Friday, confirming a report in German daily Stuttgarter Zeitung.

"It is highly doubtful that the chief executive personally can be held responsible for this, however."

The Stuttgarter Zeitung reported earlier that the parents of the 27-year old engineer felt the company should not have put the intern behind the wheel of a fast car on a test track.

"There is already a ruling from the district court in Papenburg in which the judge expressly found that Daimler could not be held at fault in any way for the accident," a Daimler spokesman added.

In a statement, the company later called the investigation a formality and said that it expects the probe to be dropped.

(Reporting by Andreas Kroener. Editing by Jane Merriman)