The failure of the Agriculture Department to respond quickly to hints of an outbreak of deadly African swine fever on two Maryland farms last year has led a public-interest group to call for changes in USDA's disease-monitoring procedures.

Internal USDA documents obtained by the Foundation on Economic Trends disclose that the Animal and Plant Health Inspection Service (APHIS) did not make complete tests and did not react quickly to the possible presence of the disease in Maryland hogs.

Jeremy Rifkin, president of the foundation, yesterday asked Agriculture Secretary Richard E. Lyng for a full review of APHIS testing procedures and renewed an earlier request that USDA activate an emergency surveillance program for African swine fever in the Southeast and Gulf states.

"If African swine fever is present in the United States, it is critical that it be identified early in order to avoid the potential of catastrophic losses to the nation's pork industry," Rifkin told Lyng. The disease is so virulent that destruction of herds is necessary.

The documents obtained by Rifkin also reflect concern among APHIS officials about the delays in reporting signs of the disease. But they show that top administrators, after some debate, decided not to intensify surveillance programs because of the cost.

The foundation's concerns were seconded by William Hess, a leading African swine fever authority, who works for USDA's Agricultural Research Service at Plum Island, N.Y.

"In view of recent events, I think we should have a closer look at the testing procedures," Hess said. "It is time to take a deeper look at the procedures and the policy."

The documents obtained by Rifkin show that serum samples taken from slaughter hogs in New Jersey last year turned up positive in both of the standard tests used to identify the presence of the disease. When both tests show positive, blood samples ordinarily are then taken for verification.

But after the apparently diseased hogs had been traced to Maryland, a USDA investigator was sent to the farms. The investigator decided from visual observation that the disease was not present and took no blood samples for further testing.

Rifkin said yesterday that although the series of memos did not mention it, APHIS later conducted blood tests on the Maryland hog herds and results were negative. But he said the reporting delays in the case justified revision of APHIS procedures.

G.J. Fichtner, a northern region veterinary services director for APHIS in New York, also protested the procedures in a memo to Washington. He complained about reporting delays and said that a field investigation should have started as soon as the first positive tests were found.

"If African swine fever had been present along the eastern coast on the date the animals were slaughtered and samples collected, there would have been the opportunity for widespread dissemination of the disease before the test results were ever available," Fichtner said.

Rifkin said concerns about African swine fever, which has never been detected in the United States, had been heightened by recent reports that an independent researcher discovered the presence of the fever-causing virus in hogs in Belle Glade, Fla.

APHIS quarantined two Florida farms and collected blood samples from the hogs, but reported this week that tests at the agency's Plum Island laboratories showed that swine fever was not present.