CONCOURSE, the Bronx — A man is now behind bars, facing up to life in prison if he’s found guilty of the felonies he’s charged with, after agents say they found a massive cache of fentanyl hidden in his gas tank.

They made the discovery on Sunday, just half a block from the Bronx Criminal Court building.

That’s where Drug Enforcement Administration agents, at around 1:40 p.m., were doing surveillance as part of a short-term investigation. They say they pulled over a red Ford Expedition with Texas license plates in front of 295 East 161st St.

An NYPD K-9 unit working with the agents alerted officers to the presence of illicit drugs in the vehicle, according to the agencies involved in the case. They said that an inspection of the driver’s phone not only showed bundles of cash, it also revealed that there was access to the vehicle’s gas tank from inside the cab.

That led agents to arrest the driver, Enrique Perez, 44.

Agents then started fishing out vacuum-sealed packets from the gas tank, through a specially made access door hidden under the rug of the SUV’s rear seating area.

New York City Special Narcotics Prosecutor Bridget Brennan has convicted hundreds of drug traffickers to prison in her nearly 25 years of handling major drug cases. Even she was surprised at the gas tank-stashed fentanyl cargo.

“I’ve never seen anything like that before,” she said in an interview.

“It tells me, number one, maybe we’re doing a better job than we might think,” she continued, “that they find they need to conceal it in a creative way. But it’s frightening that that much deadly fentanyl is being transported.”

Agents pulled out more than 11 pounds of powdered fentanyl from the gas tank, as well as 300,000 fake oxycodone pills laced with fentanyl, according to Brennan’s office. It says that the whole stash of illicit drugs has a street value of $5 million.

Prosecutors charged Perez, who lives in Columbus, Ohio, with criminal possession of a controlled substance in the first and third degrees. The first-degree charge is a felony that could result in a life sentence if Perez is found guilty. He’s being held on $200,000 bail.

The prosecutor said that his vehicle and its cache of drugs fit a pattern, where out-of-state vehicles travel to New York City, carrying loads of fentanyl, and then deliver their illicit cargo here.

The investigation shows that the drugs that Perez is accused of trafficking came from Mexico, and that his truck has crossed the U.S.-Mexico border multiple times, according to the prosecutor. The SUV Perez was driving had Texas license plates.

In addition to the Special Prosecutor’s Office, the DEA, NYPD, the Bronx Prosecutor’s Office, and the New York Organized Crime Drug Enforcement Strike Force were all involved in the investigation.

Prosecutor Brennan said that their cooperation not only leads to major busts like the one this past Sunday, but is also part of a mission to break a drug pipeline to New York City.

“If we found these drugs, we can find anything,” Brennan said, “and we will work tirelessly to make sure that our city is protected and our citizens are protected from this deadly scourge of fentanyl.”