The test performed by the New Jersey Medical Examiner's laboratory found no traces of xylene, hexane, carbon tetrachloride, methylene chloride or chloroform in the tissues of one of the dead marine mammals.
"It was a long shot, but they figured they had to try because of the rumors of a large hexane and xylene spill," said James Staples, spokesman for the New Jersey Department of Environmental Protection.
Staples said that in July there had been repeated rumors of a 450,000- gallon hexane and xylene spill off the New Jersey coast.
The Coast Guard checked the manifests of several ships and, when dolphin tissue samples became available, tests for the two chemicals and a few similar compounds were done, Staples said.
"There are so many different chemicals you could test for, there are still many chemicals that could be out there," Staples said.
One of the problems in running the tests has been a lack of fresh tissue samples. Once the animals begin to decompose - which happens within hours after death - it is almost impossible to determine the cause of death, researchers say.
The U.S. Department of Agriculture's National Veterinary Services Laboratory in Ames, Iowa, which is spearheading the lab analysis on the dolphin problem, has already rejected two sets of samples from National Marine Fisheries researchers in Virginia Beach, Va., because they were not fresh enough.
Yesterday, however, the investigation got a boost in both New Jersey and Virginia.
The Marine Stranding Center in Brigantine, Atlantic County, was advised that samples it sent to Iowa on Tuesday were suitable for analysis. "We were informed that they were the first workable samples," said center director Bob Schoelkopf.
Schoelkopf said the center was working with a team from the University of Pennsylvania's School of Veterinary Medicine to dissect the animals and provide tissue samples.
In addition, the fisheries service team in Virginia received two fresh dolphin carcasses, one possibly dead for less than 45 minutes.
Researchers quickly took blood and fluid samples, and necropsies - the animal equivalent of autopsies - were done within an hour, according to Brian Gorman, a National Marine Fisheries Service spokesman.
"It's hard to tell whether the information will be significant," Gorman said of the latest tissue samples. "We're certainly hopeful. These are the freshest animals we have obtained so far."
Gorman said that Joseph Geraci, the marine mammal pathologist heading the Virginia-based team, spent yesterday in a boat looking for animals at sea.
"This is the first step in making preparations for a live capture in the next few days," Gorman said. He explained that the team hoped to obtain blood and skin samples from a live but ailing animal. He said that an animal might also be isolated in impoundment for observation.