The first round of Mexico’s opening up of its oil sector has attracted “huge interest from private firms”, according to Energy Secretary Pedro Joaquin Coldwell.

A total of 46 companies have declared their interest, and 23 are being vetted to see if they qualify for the 15 July auction.

Mexico’s Congress approved the energy reform last year, so the monopoly on drilling held by state-run firm Pemex since 1938 is to be broken up.

A government Web site dedicated to the first round reveals that energy multi-nationals such as Chevron of the USA, France’s Total and Anglo-Dutch group Shell are involved in the bidding process. The first round involves 14 shallow-water blocks in the Gulf of Mexico.

Mr Coldwell said his government expects to receive nearly $16.8 billion in investments over a five-year period.

However, he added that the fall in oil prices has forced his administration to dramatically cut its budget and to consider whether to delay auctions for unconventional oil projects, which include harder-to-reach deposits.