By Sara Smart, Sharif Paget, Pete Muntean and Raja Razek, CNN

(CNN) — Alaska Airlines has temporarily grounded its fleet of Boeing 737-9 aircraft after one of its planes made an emergency landing in Oregon Friday, officials said – an incident that a passenger says involved a panel and window blowing out in flight.

Alaska Airlines Flight 1282, which was headed from Portland to Ontario, California, returned safely to Portland International Airport around 5 p.m. PT after “the crew reported a pressurization issue,” the Federal Aviation Administration said.

A panel of the fuselage, including the panel’s window, popped off shortly after takeoff, Kyle Rinker, a passenger on the flight, told CNN.

“It was really abrupt. Just got to altitude, and the window/wall just popped off and didn’t notice it until the oxygen masks came off,” Rinker said.

Firefighters were called to assess minor injuries after the landing, and no serious injuries were reported, the Port of Portland Fire Department said.

A passenger’s video posted to social media shows a side section of the fuselage, where a window would have been, missing – exposing passengers to the outside air. The video, which appears to have been taken from several rows behind the incident, shows oxygen masks deployed throughout the airplane, and least two people sitting near and just behind the missing section.

In a statement late Friday, Alaska Airlines said it was working with Boeing to understand what took place on Flight 1282. The aircraft is a 737 Max 9 that received its certificate of airworthiness on October 25, 2023, according to the FAA.

The airline’s grounded fleet of 65 Boeing 737-9 aircraft is expected to undergo full maintenance and safety inspections over the next several days before being returned to service, the airline said.

“My heart goes out to those who were on this flight – I am so sorry for what you experienced,” Alaska Airlines CEO, Ben Minicucci said in a statement.

Though the airline has acknowledged an incident on Friday’s Flight 1282, it has not detailed what the incident entailed. The plane “landed safely back at Portland International Airport with 171 guests and six crew members,” the airline said.

According to FlightAware, the flight was airborne for about 20 minutes. The plane departed from Portland International Airport around 5:07 p.m. local time and landed at 5:27 p.m.

Evan Smith, a passenger on the airplane, told CNN affiliate KPTV that he was sitting at least six rows in front of the section where the incident took place. “There was a really loud bang towards the rear of the plane and a whoosh noise and all of the masks dropped,” Smith said.

Emma Vu, another passenger, was asleep in her seat and woke up to a sensation of falling and seeing emergency masks drop down, she told CNN in a phone call on Friday. She apparently woke up after the panel section popped off; it wasn’t clear how close to the missing panel she was.

Vu said she texted her parents their code word for emergencies to let them know about the incident. “I’ve never had to use it before, but I knew that this was that moment,” Vu said.

People sitting on either side of her comforted her, she said. “The flight attendant came over too, and told me it was going to be OK,” Vu said. “The fact that everyone was kind of freaking out and she took that time to kind of make me feel like I was the only passenger – honestly that was really sweet.”

Vu plans to take a different flight to her intended destination on Saturday morning, she said.

The FAA and National Transportation Safety Board will investigate the incident, both agencies said.

In a statement to CNN, Boeing said it was aware of an incident involving Alaska Airlines Flight 1282 and was working to gather additional information.

CNN’s Paradise Afshar and Tina Burnside contributed to this report.