Updated at 4:35 p.m. ET
At least one person died after a Southwest plane experienced serious engine trouble Tuesday and was forced to make an emergency landing in Philadelphia. Seven other people on board Flight 1380 were injured.
"We do have information that there was one fatality," National Transportation Safety Board Chairman Robert Sumwalt told reporters during a news conference. Philadelphia Fire Department Commissioner Adam Thiel had previously told reporters that one person was transported to the hospital in critical condition and that the seven others were treated at the scene for minor injuries.
The Boeing 737-700 had 143 passengers and five crew members on board as it headed from New York to Dallas, according to the airline. (Sumwalt's number slightly differed — he said there were 144 passengers.)
The plane made the emergency landing "after the crew reported damage to one of the aircraft's engines, as well as the fuselage and at least one window," according to the Federal Aviation Administration.
Thiel told reporters that firefighters "found a fuel leak and a small fire on one of the engines."
Photos taken by passengers on Flight 1380 and others showed that one of the plane's windows was blown out and parts of an engine were ripped off.
"Something is wrong with our plane! It appears we are going down!" passenger Marty Martinez said in a live-stream video as he breathed through an oxygen mask. He said on Facebook that an explosion outside the window injured a woman sitting next to it.
Passenger Kristopher Johnson told CNN, "All of a sudden we just heard this loud bang rattling and then felt like one of the engines went out, the oxygen masks dropped.
"We just got the mask on, and as soon as we landed we were thankful. The pilots did a great job, the crew did a great job, got us down in Philly."
Southwest Airlines said it is "in the process of gathering more information" and did not immediately indicate what caused the trouble. The FAA says it is investigating the incident, which will be led by the NTSB.
Sumwalt, the NTSB Chairman, said that the federal agency is deploying a "go team" to conduct an "extensive investigation." He says that the flight recorders have been secured from the plane, and the investigators expect to receive a preliminary readout this evening. The engine will be shipped off-site for inspection, he said.
The flight tracker FlightAware shows that the plane took off from New York's LaGuardia Airport at 10:27 a.m. ET, then suddenly turned sharply toward Philadelphia, where it landed at 11:23 a.m.
Philadelphia International Airport said the plane landed safely and that passengers were taken to the terminal. It added that people on other flights to and from the airport should expect delays.
CNN video showed the plane on the tarmac as rescue workers operated around it. Firefighting foam was visible on one side of the plane.
Although the airline hasn't officially confirmed what led to the emergency landing, Aviation analyst Miles O'Brien told CNN that the images of the plane show signs of "uncontained engine failure."
He said this could mean that a piece of the engine came off and escaped from the cowling. "And this could be a very hazardous situation because essentially those are ... pieces of shrapnel that come off at very high rates of speed and can easily pierce the skin of the aircraft."
Sumwalt stated that "uncontained engine failure" is a technical term that they are not certain is accurate yet, because it would refer to shrapnel from a specific part of the engine.
"Even though we believe there were parts coming out of this engine, it may not have been in that section of the engine that technically would qualify this as an uncontained engine failure," he said, adding that they are characterizing it as simply an "engine failure" for now.
Southwest is known for its strong safety record. In fact, Tuesday's fatality appears to be the first person to have died on one of the airline's planes as a result of an accident. According to industry analyst The Points Guy, the airline has been involved in one previous incident that resulted in a death on the ground, when a Southwest plane struck three cars in Chicago as it slid off a runway. Copyright 2018 NPR. To see more, visit http://www.npr.org/.