UPDATED 7:05 PM: Just when you thought it was safe to go back in the subway.

Riders Tuesday night were startled to find a dead shark stinking up a Queens-bound N train. And how it got there is still a mystery.

Brandon Sanchez, a 20-year-old artist manager living in East Williamsburg, spotted the shark after getting on the train at Canal Street around midnight. He said the smell was so intense, he hopped onto a neighboring train car. He got off at the Union Square stop and ducked back in the car to snap a picture of the dead sea creature.

“I was pretty shocked at first,” Sanchez, an NYU student, wrote in an email. “This is definitely the weirdest thing I've seen happen on the subway.”

The gray shark was about a few feet long and was found on the train car floor beneath the seats.

An MTA spokeswoman said that a conductor got word that a dead shark was on board at around 12:30 a.m. and alerted a service supervisor at the final stop in Ditmars Boulevard. The supervisor tossed the shark in a trash bag and disposed of it. The train car was cleaned before returning to service.

Kevin Ortiz, an MTA spokesman, said on Twitter that “we're not investigating how it got there,” though he jokingly mentioned “unconfirmed reports that the shark was headed home after a night of partying in Coney Island.”Juan D. Cano, a 31-year-old project manager at an advertising agency, at first thought it was a doll for a marketing promotion.

“It's ‘Shark Week,’ it's ‘Sharknado’ — somebody's got to be doing something,” said Cano, who was riding the N train home to Astoria.

Cano got on the train at midnight after an event near Union Square and immediately noticed a rotting stench.

“It was a really potent, fishy smell,” Cano said. “You can't fake that smell.”

While train riders debated whether the shark was real, Cano grabbed the shark and flipped it on its belly.

“I touched fish before. I'm not an expert but you can tell when something's real,” he said.

Though the foul smell kept the train car empty, straphangers eventually started to ride on the car to get a glimpse of the subway shark.

“Every stop, we'd be watching the reactions of the new people walking in,” said Cano, who had fun with the stark by posing it for a photo with a MetroCard. “There were screamers and laughers.”