PORTLAND, Ore. (AP) — Fumes detected in the cabin of an Alaska Airlines flight destined for Phoenix caused pilots to head back to Portland International Airport in Oregon on Wednesday.

Officials with the Port of Portland said passengers and crew detected fumes in the cabin during the flight, KATU-TV reported. The plane landed safely.

Port of Portland spokesperson Melanni Rosales said seven people including passengers and crew requested medical evaluations. No one was taken to the hospital, according to Rosales.

Alaska Airlines said in an email that the crew of Flight 646 followed procedures and declared an emergency.

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

Port firefighters and those from Port and Portland Fire & Rescue investigated but couldn’t determine the cause of the smell, Rosales said.

The flight left Portland at 5:26 p.m., reaching an altitude of 35,000 feet (10,668 meters) according to Flightaware. It turned around southwest of Burns, Oregon, and landed back in Portland at 6:33 p.m. The aircraft was a Boeing 737-800, according to Flightaware.