TAMPA — For the uninitiated, the pungent odor that sometimes hangs in the lobby of the Tampa Police Department headquarters likely goes unidentified.

For those with experienced noses, however, the skunky aroma at One Police Center has an unmistakable dankness.

It's pot.

This is not the scent of someone smoking a joint in the stairwell. It's the odor of unburned plants and the buds that bloom on them.

"That explains why so many sit outside on those benches," Tampa Mayor Bob Buckhorn quipped through a spokeswoman.

As jarring as it might be for visitors to walk into a police station that reeks of weed, it doesn't take much detective work to figure out the source.

Partway up the 10-story building is the evidence room, where marijuana seized in investigations is stored. The odor of the herb sometimes escapes and wafts into other parts of the building.

"We've always had challenges when marijuana evidence comes in and how much it smells," said Chief Brian Dugan. "It's a problem we have with proper ventilation. At times it's really bad."

The odor gets especially strong after the narcotics detectives bust a grow house, Dugan said. Seized plants are put in sealed cardboard boxes and placed in a "dry room" at the station to dry.

The boxy building that Buckhorn calls "Big Blue" for the distinctive tint of its windows previously handled deposits of a different sort.

Opened in 1962 as Marine Bank, the structure at 411 N Franklin St. housed SunTrust Bank before Mayor Dick Greco's administration bought it in 1996 for $2.95 million and renovated it for the Police Department.

Now, a large bank vault with a massive door is packed floor to ceiling with boxes of evidence seized in drug cases. Dugan gave a Tampa Bay Times reporter a tour of the evidence room Thursday, extinguishing any doubt about the source of the smell.

The St. Petersburg Police Department has a similar problem at its aging headquarters, spokeswoman Yolanda Fernandez said. The building at 1300 First Ave. N was built in multiple phases, with the first part unveiled in 1951 and the other in 1978, Fernandez said in an email. The evidence room is in the basement of the older building, and sometimes the odor of marijuana travels up the elevator shaft to the floor above, where detectives can smell it.

"The odor comes and goes, depending on the case du jour," Fernandez said. "For example, if we bust a grow house with fresh pot, the smell is really strong."

The scent does not reach the station lobby in the newer section of the headquarters, she said.

There's another potential factor at play: As the police stations got older, pot got stinkier.

Marijuana in the 1960s and early 1970s smelled grassy because there wasn't as much oil content as now, Michael Backes, the author of Cannabis Pharmacy: The Practical Guide to Medical Marijuana, told the Chicago Tribune in 2016. Changes in how marijuana was grown and the introduction of more compact, oilier species pumped up the potency and the smell grew skunkier, Backes said.

The creeping aroma of reefer is one reason St. Petersburg's new police station will feature a property room in a separate wing with its own ventilation system, Fernandez said. The $78.5 million headquarters is expected to open in early spring.

No such plans are on the horizon in Tampa.

In 2015, Buckhorn called the police station obsolete, saying it had outlived its usefulness and had grown increasingly expensive to maintain. He said he would start planning for a replacement.

Those plans have been "put on hold for this administration," Buckhorn spokesman Ashley Bauman said this week. With Buckhorn's final term burning down, the project will be passed to his successor.

"Obviously it's a need, but there's no money for it, so you have to kind of just be realistic," he said.

In the meantime, the Tampa Police Department is taking a live-and-let-linger approach.

Dugan noted with a laugh that people who have received civil citations for possessing small amounts of marijuana pay their fine in the lobby.

"The irony of paying your civil citation in a room that smells like weed," he mused, "and it smells like the cops are all getting high."

Contact Tony Marrero at tmarrero@tampabay.com or (813) 226-3374. Follow @tmarrerotimes.