PARIS (Reuters) - Total Petrochemicals France has been put under a manslaughter investigation over a blast at a plant in eastern France that killed two people, its parent company said on Saturday.

An investigating judge in the city of Metz put the affiliate of oil group Total under formal investigation this month for alleged manslaughter and unintentional injury in relation to the July 2009 explosion at the Carling petrochemical plant, a Total spokeswoman said.

"This involvement in the investigation will allow Total Petrochemicals France to put forward its analysis of the causes of the accident," the spokeswoman said, confirming an earlier press report.

The blast occurred when workers were attempting to restart a steam cracker, a furnace that processes oil derivative naphtha for making plastics.

Local newspaper Le Republicain Lorrain earlier said the affiliate as well as the plant's former director had been placed under investigation.

A CGT union official at Carling told Reuters the judge's decision followed the submission of an expert's report on the accident.

(Reporting by Gilbert Reilhac and Gus Trompiz; Editing by John Stonestreet)