The National Marine Fisheries Service planned to take another look at the Navy’s pending request to disturb marine mammals between Imperial Beach and Coronado where it conducts amphibious and special warfare training, agency leaders told the San Diego Union-Tribune on Friday.

The Navy’s application has been in the works for years and says it does not anticipate any dolphin deaths due to training, but the fisheries service has opened an enforcement case that will seek to determine whether the Navy has violated the Marine Mammal Protection Act of 1972, a landmark law designed by Congress to safeguard dolphins, whales and similar creatures.

After a March 4 blast, the Navy found three dead long-beaked common dolphins and reported them to the fisheries service. Two other dead dolphins were found later, but it’s not clear if they were injured by the Navy exercises.

Environmentalists have called on the Navy to suspend activities involved in the deaths and conduct a transparent investigation.

But Navy officials said the program it calls “mission-critical” would continue. They said they were following proper procedures on the day of the blast and are conducting their own investigation to see if changes are necessary.

“We have an excellent track record in our training and have exacting standards that we apply to try to prevent these types of incidents,” Cmdr. Greg Hicks, a spokesman for the Navy’s Third Fleet, told the Union-Tribune. “We do our best to protect marine life while conducting essential training.”

Hicks said there were no dolphins in view when the training countdown began, and when they could be seen it was too late to stop safely.

Michael Jasny of the Natural Resources Defense Council, which years ago sued the Navy to minimize damage to whales by sonar, said the Navy doesn’t have the best environmental record when it comes to ocean life.

“There is training and there is training safely with full safeguards for the protection of the environment,” Jasny said. “They haven’t always done that.”