The gamblers took it in stride. And top-ranking casino officials didn't even bother to leave.

but the New Jersey State Police today took a bomb-extortion threat seriously enough to order the first evacuation ever of a casino in this East Coast gambling resort.

The Caesars Boardwalk Regency casino hotel was emptied of about 2,000 guests and employes this this morning but the detonation deadline passed without the threatened explosion and it was business as usual by 12:30 p.m.

"It would appear that the whole thing was just a hoax," Caesars World spokesman Herb L. Wolfe said later.

Police ordered the fully booked 504 -- room hotel cleared for 2 1/2 hours after a letter -- received late last week -- threatened the detonation of the $138 million complex. The letter demanded 6.5 million, but no bombs were found today and no money paid.

About 1,200 employes and 740 overnight guests were guietly asked to leave, including contestants in a regional Mrs. America Pageant.

Many guests were roused from sleep by a 9 a.m. call from the hotel switchboard and told nothing of the bomb threat. Those who inquired were told the reason for the ordered exodus, but few were fazed by it.

"I tell you, it's the only thing that could have gotten me out of bed by 10 a.m.," said Laurel Becker, a West End, N.J., housewife. But even at that, she did not leave her room until 11:30. "I couldn't leave without putting on my makeup," she said.

Hundreds of morning gamblers were denied entry to the gamming tables and slot machines scheduled to begin play at 10 a.m. as FBI agents, state troopers and local police waited for the deadline to pass.

Police also evacuated several shopkeepers and home owners within a two-block radius of the casino hotel.

State police and Caesars' officials refused to discuss the threat. And Caesars' was silent on the aspects of this threat that differed from the "literally hundreds received at the casino" since the advent of legalized gambling in this oceanside community two years ago.

On Jan. 28, a threatened explosion at the $130 million Harrah's Marina Hotel and Casino here, which ended with the arrest of a gun-toting Pennsylvania man, failed to alarm police officials enough to order an all-out evacuation of that complex.

Indeed, as registered guests -- none of whom canceled their stays -- wandered back into the hotel as casually as they abandoned it hours earlier hotel officials were grappling with the precedent -- setting implication of the state police's action.

It was clear hotel officials did not believe the threat warranted the "drastic" action taken at the orders of the state police. As Wolfe said, "It we thought there was a bomb, hotel officials would not have stayed in the hotel. Herb Wolfe is not known for his bravery."

Law enforcement sources said an extortionist's letter claimed 16 remote controlled explosive charges had been planted while the casino hotel was being built in 1978 and ealry 1979.

"To me the whole thing was just plain dumb," California research chemist Jerry Harlow, attending the Pittsburgh Conference of Scientists, said. "When i heard the bombs were set in place two years ago, I knew there were no batteries that could last that long.

"I don't consider this excitement. I consider this stupidity," he said, adding that the excitement is in the gambling -- which he was being denied.