Two Japanese firms and an American company were indicated by a New York grand jury yesterday for smuggling 2,500 American alligator hides to Japan and France.

The indictment culminated three years of investigation by the U.S. Fish and Wildlife Service and the U.S. Customs Service into what appears to be the largest international smuggling operation yet uncovered in violation of the Endangered Species Act.

Alligators are classified as endangered or threatened - meaning close to extinction - although they have recently been making a comeback in parts of Louisiana, Florida and other states.The fish and Wilelife Service estimates that because of strict enforcement against poachers, the population may now stand at roughly 800,000 alligators in America.

In 1969, the Endangered Species Act prohibited hunting the reptiles, whose [WORD ILLEGIBLe] are valued for watchbans. [WORD ILLEGIBLE] and purses. However, in 1975 [WORD ILLEGIBLE] hunting was reinstated in three Louisiana counties, where hides are sold at a government auction.

The 2,500 hides seized in the current case were illegally obtained from independent Louisiana trappers and secretly shipped to tanneries abroad, according to Assistant U.S. Attorney Douglas Kramer. The hides were valued at $700,000.

The companies indicted on a variety of charges, including alleged international trafficking in the hides of an endangered species, were Meg Import firm specializing in wild animal skins, Gunze New York, Inc., a subsidiary of the Japanese Gunze Sangyo Ltd., and Egawa International Co. Ltd., a subsidiary of the Japanese Union Sales Co.

Also indicted were Jacques Klapisch, head of Meg Imports; Kiyoshi Egawa, president of Egawa International; John Kelly of Queens, N.Y., and William Greenblatt of North Bellmore, N.Y., who allegedly participated in the operation.

Conviction could bring up to 10 years in prison and fines up to $20,000.