WASHINGTON — The Interior Department is endorsing seismic exploration for oil and gas in Atlantic waters, a crucial move toward starting drilling off the Carolinas, Virginia and possibly down to Florida.

The department released its final review Thursday, favoring a plan to allow underwater seismic air gun blasts that environmentalists and some members of Congress say threaten whales and dolphins.

The oil industry wants to use the air guns to find out how much oil and gas lies along the U.S. Atlantic seabed. Federal estimates of a relatively modest 3.3 billion barrels of oil date from the 1970s and 1980s and are considered too low.

“The currently available seismic information from this area is decades old and was developed using technologies that are obsolete,” said Tommy Beaudreau, the director of the Bureau of Ocean Energy Management.

The federal government wants to use the information to decide whether to open up the mid- and south Atlantic to oil and gas drilling for the first time in decades. President Obama had planned to start allowing drilling at least off the coast of Virginia, but he postponed consideration of the idea after the massive 2010 BP oil spill in the Gulf of Mexico.

The Interior Department plan is to start allowing underwater seismic air gun tests from Delaware to Florida’s Cape Canaveral.

The seismic tests involve vessels towing an array of air guns that blast compressed air underwater, sending intense sound waves to the bottom of the ocean. The booms are repeated every 10 seconds or so for days or weeks. The echoes are used to map the locations of subsea oil and gas deposits.

The Interior Department got more than 55,000 public comments on the proposal. Environmental groups warn that the blasts make whales and dolphins deaf, preventing them from feeding, mating and communicating. More than 50 members of Congress, including a few Republicans, have sent letters to the president opposing the air gun tests and saying they could injure up to 138,500 marine mammals.

Interior Department officials said their plan protects the endangered North Atlantic right whale by closing areas along its main migratory route to the air gun testing.