WINDSOR LOCKS, Connecticut (WASHINGTON POST) - Federal crash investigators have begun sifting through the debris of a World War II-era plane that crashed at a Connecticut airport Wednesday (Oct 2), killing seven people and injuring at least seven others.

The vintage Boeing B-17 went down about 10am, shortly after it took off from Bradley International Airport in Windsor Locks, Connecticut.

There were 13 people aboard, including three crew members.

The seven people who died were all adults, James Rovella, commissioner of the Connecticut Department of Emergency Services and Public Protection, said at an evening briefing.

He was joined by officials with the National Transportation Safety Board, who are leading the investigation into the crash.

Rovella said officials have notified all but three families, adding that he expected the names of the victims to be released in coming days. He declined to say whether crew members were among those who died.

He said at least two other people on the ground were injured: a firefighter who was treated at the scene and an airport employee who is being treated at a hospital.

"We'd like to extend our deepest condolences to those who lost loved ones in this event," said Jennifer Homendy, a member of the NTSB.

Homendy said NTSB investigators will spend the next seven to 10 days collecting evidence and expect to release a preliminary report shortly after.

The plane, which was owned by the Collings Foundation, was among several vintage planes that had been bought to the airport as part of a special show.

A spokesman for the Connecticut National Guard said that a member of the Air National Guard was aboard the flight and suffered minor injuries.

The governor's office confirmed that two firefighters with the Simsbury Fire District were also aboard but could not comment on their condition.

The Federal Aviation Administration said the vintage Boeing B-17 crashed while attempting to land at the airport.

The plane is a civilian-registered aircraft and is not operated by the military, officials said.

Images on television and social media showed flames and huge plumes of black smoke at the scene of the crash.

The plane took off shortly after 9.45am, according to Rovella, and crew members radioed the control tower about five minutes later that they were experiencing difficulties.

Rovella said officials from the FBI and the Department of Homeland Security are assisting in the investigation. They are being aided in the investigation by Connecticut State Police.

It was not clear whether the plane was equipped with a flight recorder, widely known as a black box, which would offer clues about what might have gone wrong.

Six people were being treated at Hartford Hospital. At least three were in critical condition, according to Kenneth John Robinson, the hospital's chief of emergency medicine.

Two patients were transferred to Bridgeport Hospital, which has a specialised burn treatment unit.

The airport was closed for about three hours, leaving hundreds of people stranded. One runway reopened shortly before 2pm.

Kevin Dillon, executive director of the Connecticut Airport Authority, said officials expect normal operations to resume Thursday. He added that they are working with the NTSB to reopen the runway where the crash happened as soon as possible.

Bradley International Airport is the second-largest airport in New England. It is located about 27km north of Hartford.

At a news conference, Governor Ned Lamont, a Democrat, pledged a thorough investigation. "These are all members of our Connecticut family," he said. "Our hearts are broken for you right now. We're going to get to the bottom of this as soon as we can."

In a statement Wednesday morning, the Massachusetts-based Collings Foundation said the plane was one of five vintage aircraft at Bradley as part of a special event.

"Our thoughts and prayers are with those who were on that flight and we will be forever grateful to the heroic efforts of the first responders at Bradley," the statement said.

It added that its "flight team is fully cooperating with officials to determine the cause of the crash of the B-17 Flying Fortress and will comment further when details become known."

According to the foundation's website, the plane was built in 1945. It was purchased by the foundation in 1986, which restored it.

According to the NTSB crash database, the plane was involved in at least one other crash in 1987, when it was caught in crosswinds after it touched down during an air show in western Pennsylvania.

The Collings Foundation organises the Wings of Freedom Tour of World War II aircraft and a similar tour of Vietnam-era planes.

The organisation takes part in "air shows, barnstorming, historical reunions, and joint museum displays," according to its website. People can also pay to fly on the aircraft.

"Our hearts go out to the loved ones of the victims. They and the public deserve to know the facts and causes of this tragic crash," Senator Richard Blumenthal said.

Blumenthal said the crash may renew scrutiny of the rules regarding operation of vintage aircraft.

Chris Murphy, a Democrat, the state's other senator, also offered condolences. "Horrible news from Bradley this morning. My heart goes out to everyone impacted by this crash," he said in a tweet.