Federal regulators on Friday approved the use of underwater sonic cannons to find oil and gas deposits off the East Coast, reopening the debate about offshore drilling along South Carolina and other states.

Drilling advocates praised the decision, hoping exploration leads to new sources of fuel, more jobs and increased revenue. Opponents warned about potential injury to marine life from the loud blasts, as well as possible harm to the coast and tourism if the move leads to drilling.

The Bureau of Ocean Energy Management approved a set of protections that exploration companies must comply with to win lease permits. The action allows companies to request permits, and effectively abandons a moratorium on exploration and drilling established decades ago. The moratorium is scheduled to end in 2017.

Acting Bureau of Ocean Energy Management Director Walter D. Cruickshank said the protections provide the highest level of safeguards while also allowing exploration.

The National Ocean Industries Association, a drilling advocate, said the decision was needed. The group called on regulators not to delay permits with "unnecessary (permitting) hurdles lacking scientific justification."

Conservationists decried the move. Michael Jasny of the Natural Resources Defense Council called the exploration leases "a gateway drug" to eventual drilling.

The issue cuts to the heart of Lowcountry coastal life, where the proposed exploration and drilling are controversial and politically charged.

Legislators largely support it. U.S. Rep. Mark Sanford, R-S.C., reaffirmed Friday that he did not object to the testing. "At least then you have a stronger feel of whether there's any need to explore," he said. "It may make it all a moot point."

In the seismic tests, crews detonate compressed air guns dragged behind ships, creating a series of blasts every 10 seconds or so to read the "echo" beneath the sea floor. The blasts have been demonstrated to deafen or injure marine mammals, such as whales or dolphins, that navigate by sonar echoes. The blasts also are suspected of injuring other marine life.

Nine companies have applied for permits to explore for oil and natural gas offshore from Delaware to Florida. All the companies want to use seismic blasts and all want to look off South Carolina.

Testing can cost $4 million or more and geology as well as earlier testing suggest there is little extractable oil or natural gas to be found here - with one exception.

There might well be large reserves of methane hydrate, a natural gas that could be a vast energy resource - or a bomb waiting to go off. The gas is encased in ice in the deep ocean, under pressure like gas in a propane tank. Removing it with current technology could be as perilous as drilling into one of those tanks.

But research removal projects already are underway in Alaska and elsewhere. With emerging technology augmenting land-based techniques, such as fracking, the United States is poised to become the largest global oil producer by 2020, according to industry investment analysts.

The bureau estimates that 4.72 billion barrels of recoverable oil and 37.51 trillion cubic feet of recoverable natural gas could lie beneath federal waters from Florida to Maine. Oil lobbyists say drilling for it could generate $195 billion in investment and spending between 2017 and 2035, creating thousands of jobs and contributing $23.5 billion per year to the economy.

Claire Douglass, director of the environmental advocate Oceana, said the decision "appears to be a folding to the pressure of Big Oil and its big money."

The exploration companies still must work their way through a lengthy federal approval process to win permits.

The approved protections include:

Steps to avoid striking marine mammals, including visual observers and passive acoustic monitoring.

Closing off areas to protect what are thought to be the main routes for migrating right whales, a species on the brink of extinction.

Consideration of conducting simultaneous seismic blasts only at a distance from each other.

But Cruickshank, when asked, couldn't say the blasts wouldn't have an impact. The bureau's environmental impact study estimates that more than 138,000 sea creatures could be harmed, including nine of the world's remaining 500 north Atlantic right whales. The protections are "aimed at trying to mitigate the effects on marine animals," he said. "We are taking every step we can that is reasonable to take."

The Associated Press contributed to this report. Reach Bo Petersen at 937-5744, @bopete on twitter or Bo Petersen Reporting on Facebook.