Sixteen Chinese firms have pledged to invest 12.8 billion yuan (2 billion U.S. dollars) in shale gas prospection over the next three years, the Ministry of Land and Resources (MLR) said Monday.

The companies won a second round of auctions for exploration rights for 19 shale gas blocks and include 14 state-owned enterprises and two private firms, according to auction results formally announced by the ministry.

The ministry will supervise the prospection and punish firms that fail to carry out work as promised, said Peng Qiming, an MLR official in charge of prospection.

Authorities will also monitor the impact of shale gas prospection and exploration on the geological environment throughout the entire process, Peng said.

China held the first round of auctions for exploratory rights for four shale gas blocks in June 2011.

The second round of auctions was held on Oct. 25, 2012, with a total of 83 enterprises participating in the auction.

A total of 26 exploitable shale gas blocks have been made available for exploration thus far, with shale gas reserves estimated to total 25.08 trillion cubic meters, according to statistics released by the MLR.