The Senate Intelligence Committee believes Gen. Omar Torrijos of Panama probably knew that high officials of his government and his own brother were engaged in illegal narcotics trafficking, Sen. Birch Bayh (D-Ind.) told a secret Senate session yesterday.

But, the Intelligence Committee concluded after a long investigation, no reliable evidence linked Torrijos personally to this illicit activity. A sanitized version of the Intelligence Committee's report to the Senate was released to reporters during the locked-door debate on drug trafficking and its possible relevance to the Panama Canal treaties.

Several senators said there were no major new revelations during yesterday's debate. Nevertheless, public release of the Intelligence Committee's conclusion that Panama's "maximum chief" turned a blind eye to illegal activities is expected to strain Panamanian-American relations, and may encourage opponents of the controversial canal treaties.

However, Carter administration officials and treaty proponents expressed hope that the drug issue would not play a significant role in the debate over approval of the treaties.Sen. George McGovern (D-S.D.), who supports the treaties, said yesterday's secret session "may have been the biggest waste of time during the 15 years I have served in the Senate," and said it proved that opponents of the treaties "have run out of arguments."

Reliable sources said the White House overrode other government agencies in agreeing to public release of the Intelligence Committee's conclusions about Torrijos personally. The agencies, presumably including the State Department, feared that naming him in this context would complicate negotiations going on right now -- intended to persuade Torrijos to accept some Senate imposed modifications to the treaties.

But the White House concluded that the committee's view of Torrijos' role would have to be stated publicly to avoid continued public debate and private innuendo from treaty opponents.

This is the relevant section of the Intelligence Committee report released yesterday:

"Some sources have provided intelligence which we view as reliable and which we believe suggests that Gen. Torrijos knew about narcotics trafficking by government officials and did not take sufficient action to stop his brother's activities."

The committee said it had seen accusations that Torrijos too was personally involved, but "no conclusive evidence that could be used in a court of law" confirmed this.

The committee confirmed previ ously published reports that Torrijos' brother Moises, now Panama's ambassador to Spain, was secretly indicted by a U.S. grand jury in 1971 for allegedly participating in a drug smuggling operation.

Last night the Justice Department opened that indictment, which accused Moises Torrijos of facilitating transshipment through Panama of narcotics which one of his associates tried to bring into the United States.

The committee report contained several previously unpublicized tidbits, including the fact that the Nixon administration offered the option of assassinating an officer of the Panamanian National Guard in 1972.

According to the report, officials in the Bureau of Narcotics and Dangerous Drugs (predecessor of the Drug Enforcement Administration) offered their chief, John Ingersoll, four options for dealing with Col. Manuel Noriega, intelligence chief of the National Guard Panama's only armed force, whom U.S. agents believed was involved in drug trafficking.

Ingersoll's aides proposed trying to discredit Noriega in Torrijos' eyes by linking him to a fictional plot to overthrow Torrijos, or trying to pressure Torrijos to dismiss him. They suggested that "powerful groups within Panama" pressure Torrijos on the issue. Or, they suggested, Ingersoll could consider "total and complete immobilization."

"The most extreme options were immediately rejected," according to the Intelligence Committee, "but some were put into action." Informed sources said that some influential Panamanians outside the government did go to Torrijos to complain about Noriega.

Noriega's name was not mentioned by the Intelligence Committee, apparently because U.S. officials feel he is now cooperating with American efforts to combat narcotics trafficking, and do not want to alienate him.

The committee report also revealed that U.S. intelligence agencies overheard one or more Panamanian officials threaten to accuse U.S. officials of demanding payoffs at a particularly tense moment of the treaty negotiations last July.

The committee conducted a detailed investigation of the possibility that "high-level members of the [U.S.] executive and legislative branches had asked for payoffs in return for arranging increases in the annuity to be paid to Panama under the Panama Canal treaty" -- an accusation that U.S. intelligence heard might be coming from Panama.

The committee found no evidence that this was so, and said circumstantial evidence offered no support to the idea. The committee passed on the charge to the Justice Department. A spokesman there said last night that no evidence had been found to suggest any impropriety by U.S. officials.

Apparently, one or more Panamanian officials threatened to expose this alleged extortion in an angry moment after reading news reports that Ambassador Sol Linowitz, chief U.S. treaty negotiator, had said the United States would retain the right to "intervene" in Panama under the new treaties.

That emotional moment passed, however, without lasting repercussions.

The Intelligence Committee said it found no evidence that "U.S. narcotics intelligence activities affected the terms of the Panama Canal agreements."

The sanitized version of its report contained very little information about what materials or informants pointed toward Torrijos' personal involvement in drug trafficking. (The Senate met in secret because the sources of this kind of information are classified.)

"The intelligence linking Gen. Omar Torrijos to drug trafficking," the committee report said, "has been largely secondhand and of varying, reliability. For example, over the years, several drug dealers have alleged that they were friends of Gen. Torrijos, that he was one of their customers, or that he protected them."

The committee appeared to put much more faith in its information linking Torrijos' brother and government associates to drug trafficking.

The Senate will continue its closed-door session on drug trafficking in Panama today.