When a member of the audience in a television studio picked Pennsylvania's daily lottery number April 24 in Pittsburgh, the number 666 came up and the state had to pay out $4.6 million.

The payout was a record for the 3-year-old daily lottery and was three times the amount of money that had been paid to play the game.

Startled state officials found out last week that there was heavy betting on all combinations of 4s and 6s April 24, and that the betting that day was 10 times higher than on the previous day.

When 666 won, the word on the street -- both among state lottery dealers and illegal operators -- was that something was fixed.

Harried state lottery officials quickly and strenuously denied that there was tampering with the lottery. They dismissed the unusually heavy play as a fluke.

Revenue Secretary Howard Cohen, whose department oversees the lottery, suggested that organized crime had floated the rumors to discredit the lottery. s

Anyway, he said, the heaviest play that day was on the number 999, not 666.

On Friday, Gov. Richard L. Thornburgh announced that, "In an excess of caution and to remove any possible question about the integrity of the lottery," he was asking the state justice department and the state police to investigate.

The lottery started eight years ago, has proved to be a gold mine for Pennsylvania. Its profits have zoomed from nearly $60 million in its first year to an expected $161 million this year, all of which is used to finance programs for senior citizens and the disabled.

Since the beginning, the lottery and the illegal numbers game have had a strange symbiotic relationship. State officials say their game has bitten into organized crime's profits, but police sources say they doubt this. Instead, they say the illegal game has just adapted to the lottery -- the illegal game often uses the state lottery number as its own.

If bookies find one number getting heavy play, they "lay off," or bet that number with the state lottery. If the number wins, the state unwittingly pay the bookies, who then pay their clients.

That is what many suspect happened on April 24.

Law enforcement sources say Michael Caserta, alleged lieutenant and chief layoff man for the reputed crime family of the late Angelo Bruno, had bets placed throughout the city on the number 666 in the lottery.

In Pittsburgh, many bookies found play so heavy that they refused to take bets on 4-6 combinations after 11 a.m.

Some Pittsburgh operators, citing the fix rumors, have refused to pay off winners.

However, lottery officials say security precautions make it impossible to fix the lottery. The daily number is drawn at 7 p.m. in the studios of WTAE-TV in Pittsburgh in full view of TV crewmen, lottery personnel and an audience.

The number is picked by a member of the auidence, who opens a lid on top of three sealed boxes, forcing a numbered ping-pong ball to be sucked through the opening by air pressure. Officials dismiss speculation that the balls could somehow have been weighted.

But if there was no fix, why was there such a heavy play on fours and sixes? State officials can only shake their heads and admit they don't know.

The real fear of state officials is that the adverse publicity could hurt lottery sales and the programs they fund. However, initial indications are that these fears are unfounded.

Last Wednesday, the day the story broke in the press, lottery sales, increased $49,000 to $1,011,000. And the next day sales jumped $52,000.