Media playback is unsupported on your device Media caption Footage shows the wreckage of the plane engulfed in flames

Two people were killed when a UPS cargo plane crashed as it approached an airport in Birmingham, Alabama, and exploded in a fireball, officials say.

The pilot and co-pilot, who were the only crew aboard, died in the incident. No-one else was hurt.

The A300 plane crashed on approach before dawn on Wednesday, said the US Federal Aviation Administration.

Officials say the aircraft went down in a grassy field near Birmingham-Shuttlesworth International Airport.

The Airbus, which was arriving from Louisville, Kentucky, was in several sections, Birmingham Mayor William Bell said.

"There were two to three small explosions, but we think that was related to the aviation fuel," he added.

'A loud boom'

Image caption The UPS plane burst into a fireball as it crashed while coming in to land in Alabama Image caption The Airbus A300 disintegrated in a field near Birmingham-Shuttlesworth International Airport Image caption The aeroplane went down in a grassy field near the airport it was due to land at Image caption Charred debris was left strewn across the field, including the package delivery firm's cargo previous slide next slide

An airport spokeswoman said their operations had not been affected by the crash. There were no homes in the area where the plane went down.

Smoking wreckage and charred debris were left strewn across the field, including the package delivery firm's cargo.

Witnesses near the airfield reported seeing flames coming from the plane before it crashed.

"It was on fire before it hit,'' said Jerome Sanders, who lives directly across from the runway.

Sharon Wilson said the plane sounded as though it was in trouble as it flew low over her house.

"It sounded like an airplane had given out of fuel," she told the Associated Press news agency.

"We thought it was trying to make it to the airport. But a few minutes later, we heard a loud boom."

In a press conference on Wednesday, National Transportation Safety Board member Robert Sumwalt told reporters that the initial investigation showed there was no distress call from the cockpit before the crash.

UPS Airlines Chief Executive Mitch Nichols said the company's thoughts and prayers were with those involved, and said the firm would co-operate with investigators.

In 2010, a UPS plane crashed in the United Arab Emirates, killing both pilots.

That incident was blamed on a cargo load of lithium batteries, which are sensitive to temperature. They caught fire, an investigation concluded.

UPS spokesman Jeff Wafford did not specify what type of cargo was on the plane involved in Wednesday's incident. The crew members' names were not released.

The plane was built in 2003 and had logged about 11,000 hours over 6,800 flights, Airbus said in a statement.