The US government on Wednesday staged its first auction of rights to drill offshore in the Gulf of Mexico since last year's catastrophic oil spill, attracting more than $337 million in bids.

ConocoPhillips and ExxonMobil led 20 firms that bid in the western Gulf sale 218, which made available 3,913 unleased blocks covering more than 21 million acres -- about the size of the state of South Carolina, the government said.

British oil giant BP -- which leased the rig where an explosion occurred in April 2010, triggering the massive spill -- participated in the sale.

"Todays lease sale, the first since the tragic events of Deepwater Horizon, continues the Obama administrations commitment to a balanced and comprehensive energy plan," said Interior Secretary Ken Salazar, who attended the sale.

"Offshore drilling will never be risk-free, but over the last 19 months we have moved quickly and aggressively with the most significant oil and gas reforms in US history to make it safer and more environmentally responsible.

"Todays sale is another step in ensuring the safe and responsible development of the nations offshore energy resources," Salazar said in a statement.

An explosion at the Deepwater Horizon rig on April 20, 2010, killed 11 people, and the Macondo well gushed oil into the ocean for 87 days, blackening the southern US shoreline and crippling the local tourism and fishing sectors.

By the time the well was capped, 4.9 million barrels (206 million gallons) of oil had spilled out of the runaway well 5,000 feet (1,500 meters) below the surface of the Gulf of Mexico.

In October, the US government slapped BP, Transocean -- the Swiss owner and operator of the drilling rig -- and US oil services group Halliburton with citations for violating oil industry regulations in what is expected to lead to massive fines.

BP -- which was ultimately responsible for operations -- has spent more than $40 billion on the disaster and could still be liable for billions in fines, compensation and restoration costs.