Detailed inspections are to be carried out at all three electricity distribution companies operating in Bulgaria, the country's Energy Minister Temenuzhka Petkova has said.

The move follows hundreds of complaints submitted by citizens from across Bulgaria who say they received two bills in January, instead of one, the minister explained in an interview with the Bulgarian National Television, while her deputy Anton Pavlov was in private station NOVA TV's morning broadcast.

Petkov revealed that as many as 67 000 customers of Austrian-based Energo-PRO received two invoices for the same period.

Both bills include a deadline until February 10, though the date of payment of the second one was changed to February 25 following an intervention from the Ministry of Energy.

"As early as today [Monday] teams will depart from the north-east of Bulgaria. There will be inspections in other electricity distribution companies [EDCs] as well," Pavlov added. Energo-PRO is in charge of operating the grid in the northeastern part of the country.

Petkova added the government was extremely cautious about electricity bills after protests that began in end-January 2013 over energy prices toppled down PM Boyko Borisov's first government.

She described as a peculiar coincidence the fact that electricity bills were now again on the agenda at the same time of the year.

Energo-PRO, Austrian-based EVN and CEZ Razprelenie Bulgaria AD, a subsidiary of CEZ group where the Czech Republic is a majority shareholder, are the EDCs operating in Bulgaria.

Last spring they were involved in a dispute with the government and the National Electricity Company (NEK), with each side hurling accusations of prolonged debts on the other.

Former Economy Minister Dragomir Stoynev (also overseeing energy in the previous elected government) had even threatened to revoke the EDCs' license if they failed to transfer millions of BGN within weeks, but later gave up his intentions.