A United Airlines plane was forced to turn around mid-flight after a passenger's portable battery pack burst into flames

• A United Airlines flight was grounded after a passenger's battery pack caught on fire.
• Cabin crew contained the fire by putting the battery in a fire bag, per The New York Times.

A United Airlines plane was forced to turn around mid-flight and return to the San Diego International Airport after a passenger's battery pack caught fire in the cabin.

An unnamed passenger's portable battery pack burst into flames around 10 minutes after United Airlines Flight 2664 took off on Tuesday morning, per NBC San Diego. The Boeing 737 plane was en route to Newark Liberty International Airport in New Jersey, an airport spokesperson named Sabrina LoPiccolo told NBC News.

United Airlines said in a statement to CBS News that the battery pack had "ignited," but did not give further details on the cause of the fire. The cabin crew managed to contain the fire by putting the battery in a fire bag, Mónica Muñoz, a spokeswoman for the San Diego Fire Department, told The New York Times.

Fire bags are also known as thermal containment bags, or burn bags, and can be used to put out fires from portable electronic devices.

A representative at the Federal Aviation Authority told Insider that the plane landed safely back in San Diego at around 7:30 a.m. local time. This was half an hour after it first took off, LoPiccolo told The Times.

The FAA told Insider it will investigate the incident.

Four people on board the flight were taken to the hospital and treated for smoke inhalation, per The Times.

"We thank our crew for their quick actions in prioritizing the safety of everyone on board the aircraft," United told CBS News.

It's unclear what exactly caused the battery to catch fire. Representatives for United Airlines and the San Diego Fire Department did not immediately respond to Insider's requests for comment.

Lithium-ion batteries power electronic devices like mobile phones and laptops. They can cause fires on planes when they overheat. These batteries cannot be packed in checked bags, but can be brought on-board in carry-on luggage, per the TSA's regulations.

In January, two passengers on Scoot flight TR993 from Taipei to Singapore suffered minor burns when a portable charger caught fire, per Channel News Asia.

And in May, a passenger's phone caught fire on board a Wizz Air flight from Budapest to Malmö, Sweden, right before it took off. The pilot was forced to turn around, return to the terminal, and evacuate all passengers on board.