Occasionally, two or three lucky ticket holders win a lottery and must split the large jackpot.

But 433 winners?

That’s what happened Saturday in the Grand Lotto in the Philippines, where the grand prize was 236 million pesos, or about $4 million.

The minority leader of the Philippine Senate, Koko Pimentel, immediately called for an investigation.

“A lot of people were really surprised … because statistically speaking this is a very rare event,” Pimentel said in a statement. “Let us take this opportunity to investigate so that our purpose is to ensure the integrity of our lotto games.”

Sen. Risa Hontiveros also supported an inquiry into the results.

“We just want to rule out any doubts in the public mind that the results have been manipulated,” she said in a statement, according to The Filipino Times.

To win the Grand Lotto, which is run by Philippine Charity Sweepstakes Office, someone must match all six numbers, which range from 1 to 55.

Guido David, a math professor at the University of the Philippines Diliman, said the odds of 433 people all matching the winning numbers in the same contest is typically about 1 in 1 followed by 1,224 zeros. He noted that there are only 17 zeros in the age of the universe in seconds.

But Melquiades Robles, the Philippine Charity Sweepstakes Office’s general manager, insisted the drawing cannot be rigged and the hundreds of winners was a natural occurrence. 

The winning numbers in the drawing were 9, 18, 27, 36, 45, 54 — all numbers divisible by nine. 

Robles said during a news conference that some people routinely bet in patterns like the one that came up Saturday. 

"Many have held on to their numbers,” he said. “It's not only good to be loyal to your wives and husbands, it's also good to be loyal to your numbers.”

The PCSO have shared photos and video on its social media of winners collecting their checks, which broke down to about $7,400 each after deductions.

“I've been betting on pattern 9, pattern 8, pattern 7 and pattern 6 for many years, and I'm thankful I just won,” one winner said.

Terence Tao, a math professor at UCLA, told BBC News that it’s rare for any single lottery to have winning numbers in a pattern like Saturday’s Philippine contest.

"But there are hundreds of lotteries every day around the world, and statistically it would not be surprising that every few decades, one of these lotteries would exhibit an unusual pattern," he said.