A lawyers' grievance committee in New York City has started checking into Mark Lane's conduct during the ill-fated trip of Rep. Leo J. Ryan to the Peoples Temple camp in Jonestown, Guyana, last fall.

The preliminary inquiry was touched off by a Nov. 24 article in The Washington Post quoting Lane as saying he had been warned beforehand that grilled cheese sandwiches served to the Ryan party might have been laced with tranquilizers or other drugs.

"But instead of warning anyone of that possibility, Lane said later that he simply did not eat the sandwiches," Washington Post reporter Charles A. Krause wrote.

Saying that he was "shocked to read about Mr. Lane's apparent misconduct," Washington attorney Jack C. Sando wrote to court officials in New York and urged a review of Lane's qualifications "to continue as a member of the bar of the State of New York."

"If the facts are as reported," Sando protested, "Mr. Lane's conduct is an ugly stain on our profession."

The complaint, which ultimately could lead to Lane's disbarment in New York if it is sustained, was referred to the Joint Bar Association Grievance Committee with jurisdiction over lawyers in Brooklyn. It has already asked Lane for his account of the episode and must now decide whether to move ahead with a formal investigation.

Lane, who was graduated from law school in Brooklyn and joined the bar in New York years ago, said in a telephone interview from his home in Memphis last night that he had sent a written reply to the Grievance Committee denying any improprieties. Lane insisted that he had been misquoted. He said he "never saw any grilled cheese sandwiches" that day, and would have had no reason to think they might be doped.

Lane was representing Peoples Temple leader Jim Jones "in various matters" during the Ryan trip to investigate conditions at the cult's Jonestown settlement. Several hours after the lunch, Ryan, a California Democrat, and four others were shot to death at a nearby airstrip. More than 900 Temple members died at the camp the same day, many of them after drinking a concoction laced with cyanide. Jones was found shot to death, an apparent suicide.

In his complaint, which he confirmed yesterday, Sando cited canons of the American Bar Association's Code of Professional Responsibility that he felt had been violated.

One requires lawyers to "assist in maintaining integrity and confidence in the legal profession." It is accompanied by a set of disciplinary rules saying in part that lawyers "shall not engage in conduct involving dishonesty, fraud, deceit or misrepresentation... (or) engage in any other conduct that adversely reflects on his fitness to practice law."

Another canon states that lawyers should represent their clients zealously but "within the bounds of the law."

Krause quoted Lane as telling him, in a telephone interview Thanksgiving Day after both and returned to the United States from the Jonestown trip: "I brought along some cough drops which have a lot of sugar in them. I sure as hell wasn't going to eat the cheese sandwiches."

Despite Lane's reported disclaimers to the Grievance Committee, Krause, who is vacationing in Michigan, said the quotations were accurate and he added that Lane volunteered the remarks in the course of a friendly discussion about whether Krause had eaten one of the sandwiches.

"I said yes, and he proceeded to tell me why he asked," Krause said. He said he suffered no ill effects and suspects there was nothing in the sandwiches despite Lane's suspicions.

San Francisco lawyer Charles R. Garry, the Temple's chief lawyer who made his way through the jungle with Lane, said Lane turned to him at one point during their flight and said: "Charles, you shouldn't have eaten the cheese sandwich.'" Garry, who had been at odds with Lane, said he asked him why he hadn't spoken up earlier. He said Lane replied, "'Because we weren't speaking.'"