December 19 (SeeNews) - Bulgarian railway company BDZ Passengers, part of state-owned railway group BDZ Holding, has signed a contract worth 91.2 million levs ($51 million/46.6 million euro) with the Siemens Tron consortium, led by Siemens Mobility, for the purchase and maintenance of another ten Smartron electric locomotives, the ministry of transport in Sofia said.