Navy officials said that a review of the July 3 incident indicates that two ships turned on their sonar between 6:45 and 7:10 a.m., by most accounts just before the unusual movement of almost 200 deep-water whales to the shoreline of a Kaua'i bay. The Navy had said earlier that no sonar was used until more than 90 minutes later, well after the animals came ashore.

Lt. Cmdr. Greg Geisen, the Navy spokesman responsible for information about the maneuver, said a Navy review of the incident still concluded that the ships were either too far from the whales or were using the sonar at the wrong time to cause the mass movement.

"There is no evidence of a relationship here between the sonar use and the whale behavior," he said.

But the newly released information from Geisen and other Navy officials — that the ships were testing their sonar in preparation for the maneuver on the day before the whales came ashore, and early on the morning of the near-stranding — has caused some observers to question that conclusion.

"Every time the Navy changes its story, it reduces its credibility on this issue," said Cara Horowitz, a lawyer with the Natural Resources Defense Council, which has sued the Navy over a related sonar issue. "The Navy would be better off spending more time developing commonsense ways to protect whales from sonar and less time denying a connection that has unfortunately been repeatedly shown."

Officials at the National Oceanographic and Atmospheric Administration (NOAA), which is looking into the incident, said it remains uncertain what caused the near-stranding.

"At this point, we still know very little about what might have made those whales behave so unusually," said Donna Wieting, chief of the Marine Mammal Conservation Division of NOAA's National Marine Fisheries Service.

"But saying that sonar played no role might be a premature determination," she said. "Even if we can't establish a clear cause and effect, we're having these coincidences [of unusual and sometimes deadly] marine mammal behavior around sonar, and we have to ask why."

Some marine mammals come to shore naturally, because they are following a sick lead animal or trying to avoid predators and such natural occurrences as potentially harmful red tides. Melon-headed whales are relatively small and highly social animals that normally live in deep waters, at least 15 miles from shore. Wildlife officials said it is highly unusual for such a large number of them to come to shore as they did on July 3, although there is one report of a similar mass movement in the 1850s.

The new Navy information about when the sonar was used off Hawai'i was first made public in late July, at a meeting of the federal Marine Mammal Commission focused on how to limit the effects of ocean noise on whales and other sea creatures. Rear Adm. Steven Tomaszeski updated the information then, and said the Navy had concluded there was no connection between the sonar use and the unusual whale behavior.

He and Geisen said the July 2 sonar use could not have caused the whales to head into Hanalei Bay because the ships — four Japanese and two American — were too far away when the equipment was used. Geisen also said the Navy first learned of the stranding from the National Marine Fisheries Service at 5:30 a.m. on July 3, and not between 7 and 7:30 a.m., as earlier reported, making it impossible for the 6:45 to 7:10 a.m. sonar usage to have harmed the whales.

Wieting of fisheries service said, however, that her office has received no reports of a 5:30 sighting, and still believes the whales were first seen after 7 a.m.

Navy officials are adamant about the need for sonar training. They say there is a substantial and growing threat from "quiet" diesel submarines that could menace the United States from coastal waters, and that only active sonar use can detect them. The Navy is planning a sonar training ground in the Atlantic Ocean, off the Carolinas.

Residents and government officials worked throughout July 3 to steer the whales back to open water, and all made it except one newborn calf that died of starvation. Officials say that some of the animals may have died at sea without a trace.

The Hawai'i incident is the third significant one involving sonar and marine mammal strandings near the United States since 2000. The stranding of 17 whales of various kinds off the Bahamas in 2000, which resulted in the death of at least six of them, occurred during a major Navy maneuver. Navy officials at first said there was no connection between their exercise and the stranding, but later acknowledged that the loud sound from the sonar had caused the animals to flee ashore.

Another incident occurred off the coast of Washington state last year, where harbor porpoises unexpectedly came ashore after a sonar exercise. The Navy concluded that there was no connection between the two, but NOAA is still reviewing the incident.