The riots, mostly in New Delhi, started after the assassination of Prime Minister Indira Gandhi by Sikh bodyguards. The mob retaliation killed more than 3,000 Sikhs.
The investigation report was presented Monday to Indian parliament. It indicated that local Congress leaders and workers had either incited or helped the mobs in attacking the Sikhs, the BBC reported.
Among those named in the report is Jagdish Tytler, a minister in the present Congress-led coalition government. The report said there was "credible evidence" against Tytler "to the effect that very probably he had a hand in organizing attacks on Sikhs."
But a separate government report said the inquiry was not absolutely sure about Tytler's involvement in the attack."
The judge's report also said there was "absolutely no evidence" that Rajiv Gandhi, former prime minister and son of Indira Gandhi, had suggested or organized attacks on the Sikhs.