A federal investigation into snake smuggling, involving hundreds of thousands of dollars worth of rare reptiles and some of the nation's leading zoos, including Washington's National Zoological Park, is expected to end in two to three weeks with 20 to 35 indictments, according to sources close to the case.

The two-year investigation, which has ranged around the world, including Australia, Thailand, Ceylon, Singapore, France and Switzerland, is now before a federal grand jury in Philadelphia.

Some of the world's most exotic and valuable reptiles are involved: They include the green tree python, the Fiji boa constrictor and Mackloth's python.

One U.S. government source involved in the prosecution called it "the most important wildlife case ever."

The reptiles allegedly were taken in violation of the animals protection or tax laws of foreign nations. The probe facusses on violations of the Lacey Act, which prohibits interstate transportation of illegedly taken wildlife.

Herpetologists lescribed the snakes as both expensive and extremely rare in American zoo collections. A gree tree python is reportedly worth $400 on the wholssale wild animal market sources said.

Several of the reptiles are so rare that the government has found it necessary to subpoena several snake curators to identify them.

Sources said that "zoos all over the country" were involved as well as private snake collectors and roadside zoos. One source said that a total of 11 zoos are involved along with the National Zoo: The Philadelphia Zoological Garden, the Dallas Zoo, The St. Louis Zoological Park, and the Knoxville (Tenn.) Zoological Park.

Edward H. Kohn, deputy director of the National Zoo, said he did not know whether any of the reptiles involved in the investigation "are presently in the zoo's collection."

Kohn added that "the National Zoo has never knowingly acted to circumvent the federal law in any way, shape or form and I'm confident that is the case with regard to this present investigation."

In addition to the snakes, other reptiles involved include Fiji Island iguanas, which sell for $600 a pair; green tree monitors, a species of lizard valued at $500 apiece; Papuan monitor lizards and Johnson's crocodiles, a rare freshwater reptile found in Australia.

Henry Molt Jr. of the Philadelphia Reptile Exchange told the Associated Press in an interview that authorities had seized his records more than two years ago, Molt and a number of curators and zoo directors said they believed the investigation resulted from a variety of divergent interpretations of the Lacey Act.

Dr. James Bacon, curator of reptiles at the San Diego Zoo, which does not appear to be implicated, said there was a thriving black market in rare animals.

Bacon noted that zoos are subject to fads, and said the reptiles under investigation "happen to be in vogue."

One federal source said that both foreign and domestic wild animal dealers which involved and that some major names in the business were included among them.

The source also said that U.S. Customs agents had seized several reptiles that had been killed by the smugglers to avoid detention and that they would be introduced as evidence when the case comes to trial.