Doug Stanglin

USA TODAY

At least 16 people aboard a hot air balloon died Saturday when it apparently caught fire and crashed in a corn field in central Texas, in the deadliest such accident in the USA in decades.

Caldwell County sheriff's deputies responding to a 911 call about an apparent vehicle accident instead found the burned basket portion of a hot air balloon, the sheriff's office said in a statement.

The balloon crashed into farmland under a stretch of high-power electrical transmission lines in a field outside the town of Maxwell, about 30 miles south of Austin. Authorities did not immediately say what caused the crash.

A look at the deadliest hot air balloon accidents

The accident occurred shortly after 7:40 a.m. local time, Lynn Lunsford with the Federal Aviation Administration said in a statement. Investigators with the FAA and the National Transportation Safety Board were en route to the scene. The FBI office in San Antonio said Saturday afternoon that it would assist the NTSB in the investigation.

Erik Grosof of the NTSB said at a news conference Saturday that a "significant" investigation will be conducted. He would not provide an exact number of dead, only saying there were a "number of fatalities" and a "significant loss of life."

Earlier, the Texas Department of Public Safety confirmed 16 people were killed. The sheriff's office said at least 16 people were on board the balloon and it appeared there were no survivors.

More federal officials will arrive to the scene Sunday, Grosof added. Local officials will release the names of the pilots and passengers in Saturday's crash in Texas after notifying relatives. Texas Gov. Greg Abbott issued a statement to ask "all of Texas to join us in praying for those lost."

Heart of Texas Hot Air Balloon Rides owned and operated the balloon, according to the Austin American-Statesman. The company's website says it services the Austin, San Antonio and Houston areas with up to 24 people allowed on a flight.

Margaret Wylie, who lives about a quarter-mile from the crash site, told The Associated Press she was letting her dog out early Saturday when she heard a “pop, pop, pop.” She said she called 911.

“I looked around and it was like a fireball going up,” she said, noting the fireball was located under large power lines.

Fatal accidents like this are "very rare," said Dean Carlton, president of the 2,100 member Balloon Federation of America. “It’s been a pretty tough day for our community,” he said, adding hot air ballooning is “safe, fun entertainment."

Deadly hot air balloon crash in Texas raises safety questions

Between 1964 and 2013, the NTSB investigated 760 hot air balloon accidents in the U.S., of which 67 were fatal. Carlton said accidents typically occur due to a variety of factors, including wind, weather and crashing into power lines.

The FAA regulates hot air balloons, which use propane gas to heat the air that rises into the balloon and lifts it, as it regulates any other aircraft. Hot air balloon pilots must be certified and the balloons must have an air worthiness certificate. The FAA inspects the balloons used for commercial ventures after 100 hours of flight time or at least once a year.

Before Saturday, the deadliest air balloon accident in recent decades in the U.S. occurred in Aspen, Colo., in August 1993, when six people were killed when a balloon hit a power line, tearing off the basket and sending it plunging 100 feet to the ground.

One of the deadliest air balloon disasters on record occurred in Luxor, Egypt, in February 2013 when a ballon caught fire and plunged 1,000 feet to the ground, crashing into a field and killing at least 19 foreign tourists.

Fatalities have been rare in the U.S. in the past five years. In May 2014, three people died when the balloon they were on struck a power line and burst into flames during a landing attempt at a Caroline County, Va., festival. In March 2012, a balloon pilot died after his balloon was unable to climb over a fast-developing hail storm and crashed into the woods in Fitzgerald, Ga.

The hot air balloon capital of the USA is Albuquerque, N.M., Carlton said, because it has the largest collection of pilots and a unique micro climate that’s dry most of the year, making it easy to fly in the morning.

Contributing: Jefferson Graham