An Alaska Airlines flight was forced to turn around shortly after takeoff and return to Portland International Airport on Wednesday after passengers reported smelling an odor in the cabin, officials said.

The crew aboard Alaska Airlines Flight 646 from Portland to Phoenix followed procedures and declared an emergency after "an odor was detected on board," a spokesperson for the airline told Fox News Digital in a statement. The plane then landed safely at the airport.

"Guests deplaned and boarded a different aircraft to continue on their way to Phoenix," the statement said. "The aircraft in question is being inspected by our maintenance team. We apologize to our guests for the inconvenience."

Portland Fire and Rescue said passengers in the rear of the plane reported smelling "some fumes or an odor," according to FOX12 Oregon. Firefighters, however, did not detect anything when inspecting the aircraft and used thermal imaging to check for fires or other hazards.

As of Thursday morning, it remained unclear what kind of odor the passengers detected or what caused it.

While no one was hospitalized because of the incident, a Port of Portland spokesperson told the station that seven crew and passengers requested medical evaluation at the scene.

The aircraft was a Boeing 737-800, according to Flightaware. 

The incident comes two months after a door panel blew off an Alaska Airlines Boeing 737 Max midflight, sparking scrutiny over airline safety.