The reported caviar scandal that led to a massive shakeup of the Soviet fisheries ministries nearly two years ago has now spread to other institutions, leading to a wave of arrests in the Ministry of Foreign Trade, reliable sources have reported.

An investigation reportedly also spread to the Soviet Far East fleet, which presumbably was involved in the transport of the smuggled caviar to Japan.

The sources also said that a deputy Fish Industries Ministry chief, who was reportedly implicated in what is said to have been a multimillion dollar operation shipping caviar abroad marked as "smoked herring," died while in custody in the complex case.

According to these unofficial Soviet sources, Deputy Minister Vladimir I. Rytov died in prison last spring and party members were forbidden by secret instructions from attending his funeral. One knowledgeable source said there were reports Rytov had committed suicide, but his was impossible to confirm.

There has been no public notification of Rytov's reported death, and a spokesman at the Fish Industries Ministry said Rytov had "not worked here in two years and there is nothing more I will say."

The smuggling operation appearently involved hundreds of Soviets, from humble Caspian Sea fishermen to senior government officials in an operation that reportedly lasted through the 1970s and netted millions of dollars in illegal hard currency.

The ring is said to have conspired to divert precious black caviar taken from Caspian Sea sturgeon, packed it into large cans labeled "smoked herring," and shipped it to Western Europe and Japan where it was eventually resold at world prices of about $100 per ounce. The Soviets are said to have divided the profits with their foreign contacts and banked the money in secret savings accounts to be used when senior conspirators made trips abroad.

The plot was uncovered about two years ago, it is reliably reported, when some of the cans accidentally were shipped into domestic fish markets and a police investigator began probing how the large can of herring he had bought turned out to full of scarce caviar.

The Soviets have never officially acknowledged the scandal but Fish industries Minister Alexander A. Ishkov was "retired" two years ago and a full-scale shakeup carried out in his ministry. Now, the sources said, another senior official, identified as Yefim B. Feldman, deputy chief of sales administration, has been implicated and is cooperating with the authorities.