NASHVILLE, Tenn. (WKRN) — Several days after a concourse at Nashville International Airport (BNA) was evacuated amid reports of “noxious fumes,” airport officials have shared what exactly was to blame.

BNA said the initial calls about “an unpleasant odor” in Concourse C near Tootsies came in just before 2:45 p.m. on Sunday, April 16. Passengers and employees were evacuated from the concourse by Airport Operations and Department of Public Safety (DPS).

By 2:55 p.m., members of the Nashville Fire Department were dispatched to the airport to respond to “something airborne causing breathing problems,” according to officials. Photos and videos shared with Nexstar’s WKRN showed emergency responders gathering on the tarmac outside the concourse and walking through the airport with masks and oxygen tanks.

The FAA also issued a ground stop for a short time to allow emergency crews to operate safely.

According to BNA, the fire department conducted air quality testing, found no hazardous contaminants in the air, and determined it was safe for people to return to Concourse C shortly before 4 p.m.

Officials said DPS reported a brown liquid sprayed onto the dust wall near a trash can at the start of the concourse.

In a statement released Sunday evening, the airport said chemical samples taken by the fire department revealed the substance involved in the incident was butoxyethyl acetate, a solvent commonly used in lacquers, varnishes, enamels, and resins.

BNA reported Wednesday that DPS determined the source of the irritant was actually bear spray.

A passenger had reportedly realized bear spray was in their backpack after leaving the TSA checkpoint, so they tossed it in a trash can before boarding their plane.

Officials said video footage showed a custodian going through the trash, discovering the bear spray, and accidentally activating the canister.

“Nashville International Airport is committed to the safety of its passengers, staff, and airline partners. We take these matters seriously,” BNA said Wednesday. “Research was a critical component of this incident to understand the full scale of the situation to keep the public informed – as details unfolded. We will continue our efforts to provide an optimal experience for all travelers.”

Bear spray is not permitted in carry-on or checked bags, according to TSA.

In a statement Wednesday, TSA said the bear spray was “missed during the security screening of a passenger’s carry-on bag.”

“TSA takes its role in transportation security and this situation very seriously and is continuing to review details with our airport partners to ensure appropriate corrective actions are taken.”