A Washington-based Pakistani businessman, who handed out a $1 million tip to a nightclub waitress and two $500,000 checks to disco dancers, has stirred up a furor in Dallas and sparked a criminal investigation.

At the center of the Dallas controversy is a man who identified himself to Texas authorities as F. Masood Khan. His $2 million in checks - passed out at a fashionable Dallas nightclub, called Elan - later proved to be worthless, authorities said.

"It was all a big hoax," Gary Nail, a manager at Elan, said in a telephone interview yesterday. The $1 million check was meant as a tip for a waitress who helped Khan arrange a disco contest Monday night and the two $500,000 checks were intended as prizes for the winning dancers.

Khan's check writing activities are under investigation by the Dallas district attorney's office. "We're concerned about who he (Khan) really is and what's going on," said John Roach, an assistant Dallas district attorney. "We're not sure that we have."

Khan could not be reached yesterday for comment in Dallas or in Washington.Roach said Khan had claimed to be connected with the Pakistani government and had identified himself as an employe of the government-controlled National Construction Co. of Pakistan. In Washington, a Pakistan Embassy spokesman said Khan was neither a government official nor a National Construction Co. employe.

The Dallas nightclub is owned by the same company that owns Elan at 2020 K St. NW here. Guy Bowman, a floor manager of the Washington Elan, said yesterday that Khan was not listed as a nightclub member here and that Elan officials in Washington did not know him.

In addition to distributing the checks at the Dallas nightclub, Khan is also said by Dallas authorities to have tried unsuccessfully to buy hundreds of thousands of dollars' worth of furs, jewelry and otehr merchandise at several Dallas shops, including the Neiman-Marcus Co. department store. All the stores refused to extend him credit, officials said.

At the Dallas nightclub, Khan is reported to have also bought more than $2,300 worth of champagne and liquor and to have given Elan's entire staff a $10,000 tip. Elan manager Nail said that Khan's $2,365.30 check for drinks proved to be valid, but that the additional $10,000 check for tips was found to be worthless when inquiries were made at the bank at which the check was drawn.

Khan's spending spree has gained widespread publicity in Dallas. Yesterday's front-page newspaper headlines in Dallas said, "Bubble Bursts in Big Spender's Saga" and "Pakistani $2 million in Gift Checks a 'Joke.'" Dallas authorities said they were told by Khan's bodyguard that the checks were meant as a "joke." They said Khan himself had refused to answer their questions.