Bulgaria's police on Friday seized documents from the offices of public natural gas supplier Bulgargaz as part of a check into its pricing policy and trading activities, Bulgargaz said.
Bulgargaz is cooperating fully with the authorities, it said in a statement.
Earlier this month, finance minister Assen Vassilev said that Bulgargaz has been drawing from the Chiren gas storage cheap natural gas in order to export it at a higher price abroad, instead of selling it on the domestic market in a move to calm down soaring prices.
Bulgargaz officials have denied the accusations.
Wholesale prices of natural gas on the Bulgarian market increased by 30.4% in January, reaching 133.41 levs ($78.1/68.2 euro) per MWh.
Bulgarian energy regulations require Bulgargaz to set the gas price monthly. The energy regulator then has the final say on the proposed changes in the wholesale price, at which the state-owned company sells natural gas to end-suppliers and customers directly connected to its transmission network.