WASHINGTON - A hot air balloon carrying 16 passengers in the US state of Texas crashed after catching fire on Saturday, authorities said.

"The balloon was occupied and it does not appear at this time that there were any survivors of the crash," Caldwell County Sheriff Daniel Law said in a statement, according to NBC News. "Investigators are determining the number and the identities of victims at this time."

The Federal Aviation Administration said the hot air balloon crashed into a pasture near Lockhart.

Emergency responders reported the fire likely occurred in the basket portion of the balloon, the Lockhart Post-Register reported.

AFP adds: The accident took place shortly after 7:40 am (1240 GMT), when the balloon crashed into a field near Lockhart, around 50 kilometres south of Austin, Lynn Lunsford of the Federal Aviation Administration (FAA) said in a statement.

NTSB lead investigator Erik Grosof did not confirm the number of deaths or injuries, telling reporters only that "right now we have a number of fatalities." Texas Governor Greg Abbott offered condolences to those affected by the crash. "Our thoughts and prayers are with the victims and their families, as well as the Lockhart community," he said in a statement.

A photo posted on social media apparently depicting the accident showed a balloon in the air with huge flames spurting underneath.

If all 16 fatalities are confirmed, the crash would be the deadliest US hot air balloon accident on record, according to the NTSB. Previously, the highest number of fatalities in a single hot air balloon crash was six.

Hot air balloon crashes are rare in the United States. The NTSB investigated 760 such accidents between 1964 and 2013. Of those, 67 were fatal.

Three people died in May 2014 during an air balloon festival in Virginia when a balloon hit a power line and burst into flames while landing.

Hot air balloons use propane gas to heat air that keeps them afloat. They are regulated by the FAA, which requires balloon pilots to be certified and for balloons to have air worthiness certificates.

The FAA inspects the balloons used for commercial ventures after 100 hours of flight time or at least once a year.