The new government in Nigeria is reviewing contracts of oil blocks awarded in the last couple of years after it received complaints of irregularities in their allotments with some quarters expressing apprehensions that the licences won by the ONGC-Mittal combine may also be under scanner."We are reviewing award of blocks by the previous government...there were complaints about the procedures used in some of the blocks, and we are now investigating that," Nigeria's Minister of State for Energy (Petroleum) Odein Ajumogobia said on the sidelines of OPEC summit here.Although the identities of the blocks as well as the awardees are not immediately known, industry sources said some domestic and foreign entities that obtained licences to explore oil in the energy-rich African nation through 'back door' may end up losing them."I dont remember if the (two) blocks awarded to ONGC-Mittal (combine) is also under review," Ajumogobia said when asked if ONGC Mittal Energy's Block 285 and 279 were under scanner.OMEL, an equal joint venture of Oil and Natural Gas Corporation (ONGC) and steel baron Lakshmi N Mittal, had, in 2005, won rights to explore in OPL 279 and OPL 285 after committing to invest $6 billion in a 1,80,000 barrels per day greenfield refinery, a 2,000 Mw power plant and a railway line from east to the west of Nigeria.OMEL paid a signature bonus of $50 million dollars for OPL 285 and $75 million for OPL 279.In a subsequent licencing round, which happened just before elections that saw the formation of a new government, OMEL was given preferential bidding rights for yet another block (OPL 250) but it did not submit any bid.(Reporting by Ammar Zaidi)