Alaska Airlines has grounded all its Boeing 737-9 aircraft, hours after a window and a piece of fuselage on one plane blew out in mid-air, forcing an emergency landing in Oregon.

The incident occurred shortly after take-off from Portland and the gaping hole caused the cabin to depressurise.

Flight data showed the plane climbed to 16,000ft before returning to Portland International Airport. The airline said the plane landed safely with 174 passengers and six crew members.

“Following tonight’s event on Flight 1282, we have decided to take the precautionary step of temporarily grounding our fleet of 65 Boeing 737-9 aircraft,” Alaska Airlines chief executive Ben Minicucci said in a statement.

“My heart goes out to those who were on this flight – I am so sorry for what you experienced.”

The aircraft will be returned to service after full maintenance and safety inspections, which Mr Minicucci said the airline expected to be completed within days.

“We are working with Boeing and regulators to understand what occurred tonight, and will share updates as more information is available,” he said.

The airline provided no immediate information about injuries, but KPTV reported that according to the Port of Portland, the fire department responded and treated minor injuries at the scene. One person was taken for more treatment but was not seriously hurt.

The plane was diverted about about six minutes after taking off, according to flight tracking data from the FlightAware website.

The pilot told Portland air traffic controllers the plane had an emergency, was depressurised and needed to return to the airport, according to a recording by the website LiveATC.net.

A passenger sent KATU-TV in Portland a photo showing the hole in the side of the plane next to passenger seats. Video shared with the station showed people wearing oxygen masks and passengers clapping as the plane landed.

Passenger Evan Smith was on the flight and described the moment the blowout occurred, saying: “You heard a big loud bang to the left rear. A whooshing sound and all the oxygen masks deployed instantly and everyone got those on.”

He said a boy and his mother were sitting in the row where the window blew out, adding that the boy’s shirt was sucked off him and out of the plane.

The National Transportation Safety Board said it was investigating an event on the flight and would post updates when they are available. The Federal Aviation Administration also said it would investigate.

The Boeing 737-9 Max involved in the incident received its certification two months ago, according to online FAA records.

The plane had been on 145 flights since entering commercial service on November 11, said FlightRadar24, another tracking service. The flight from Portland was the aircraft’s third of the day.

Boeing said it was aware of the incident, working to gather more information and ready to support the investigation.

The Max is the newest version of Boeing’s 737, a twin-engine, single-aisle plane frequently used on US domestic flights. The plane went into service in May 2017.

Two Max 8 jets crashed in 2018 and 2019, killing 346 people and leading to a near two-year worldwide grounding of all Max 8 and Max 9 planes. They returned to service only after Boeing made changes to an automated flight control system implicated in the crashes.

Last year, the FAA told pilots to limit use of an anti-ice system on the Max in dry conditions because of concern that inlets around the engines could overheat and break away, possibly striking the plane.

Max deliveries have been interrupted at times to fix manufacturing flaws. The company told airlines in December to inspect the planes for a possible loose bolt in the rudder-control system.