WARSAW -- Polish prosecutors on Monday indicted seven people with corruption, including public officials and gas company employees, in connection with licenses to explore and exploit shale gas deposits in Poland.

"These seven people, three officials from the environment ministry, an employee of the Polish Geological Institute and three gas company representatives, were handed a total of 11 charges of active and passive corruption," Warsaw prosecution spokesman Mariusz Pieczek said.

Pieczek did not specify which firms were involved.

The three environment ministry officials allegedly accepted bribes from the gas companies to write out their tender bids for prospecting and exploitation licences, according to the TVN24 news channel.

The seven people, all Polish according to the channel, include a former director of the ministry's licensing department and a manager from DPV Service, a Polish subsidiary of Hungarian natural gas distributor Emfesz.

According to the prosecution, the bribes ranged from 13,000 to 55,000 zloty (3,000 to 13,000 euros, (US$4,000 to $17,000). The accused could face up to eight years in jail if found guilty.

Poland uses about 14 billion cubic meters of natural gas a year, of which 60 percent is imported from Russia.

The EU member of 38 million people plans to invest 12.5 billion euros in exploration and development of its shale gas sector by 2020.

At most, Poland could have up to 1.92 trillion cubic meters (67.8 trillion cubic feet) of exploitable shale gas deposits, according to the Polish Geological Institute.

Copyright Agence France-Presse, 2013