Authorities would not confirm the exact number of deaths, but Lynn Lunsford with the Federal Aviation Administration said the balloon was carrying at least 16 people and the Caldwell County Sheriff's Office said in a statement that it didn't look like anyone survived. 

If 16 people were killed, it would be the one of the worst such disasters, possibly the worst in U.S. history. The deadliest such disaster happened in February 2013, when a balloon flying over Luxor, Egypt, caught fire and plunged 1,000 feet to the ground, crashing into a sugar cane field and killing at least 19 foreign tourists. 

Saturday's crash happened at about 7:40 a.m. in a pasture near Lockhart, which is about 30 miles south of Austin.

Officials Believe No Survivors in Texas Balloon Crash

Authorities say they believe there were no survivors when a hot air balloon carrying at least 16 people caught fire an crashed near Austin Saturday. (Published Saturday, July 30, 2016)

Erik Grosof with the National Transportation Safety Board said at a brief news conference Saturday that there are a "number of fatalities" but would not provide an exact number. He said there is "significant loss of life."

Authorities have not said where the hot air balloon was based out of or which company was flying it. But NBC News reported the balloon was operated by Heart of Texas Hot Air Balloon Rides, according to the owner of the company's Facebook account. Heart of Texas Hot Air Balloon Rides has a Better Business Bureau rating of D+. The rating is mostly due to customers' complaints about canceled flights.

Margaret Wylie lives about a quarter-mile from the crash site and told The Associated Press that she was letting her dog out Saturday morning when she heard a "pop, pop, pop." 

"I looked around and it was like a fireball going up," she said, noting that the fireball was located under large power lines and almost high enough to reach the bottom of them. 

Wylie, who called 911, said the weather seemed clear and that she frequently sees hot air balloons in the area.

Chris O'Neil, an NTSB spokesman, said it was "far too early to speculate about cause." 

"We go through our investigative process without any preconceived notions," O'Neil told NBC News. "The facts lead us where they lead us."

O'Neil said 13 investigators had been dispatched to Texas, and a preliminary report would be released within 10 days. A conclusive report on the crash could take more than a year.

Texas DPS Officials Discuss Fatal Hot Air Balloon Crash

Texas Department of Public Safety officials hold a news conference to discuss a fatal hot air balloon crash near Austin Saturday. (Published Saturday, July 30, 2016)

Grosof said the federal agency has deemed it a major accident and a full-bore investigation will begin Sunday when more federal officials arrive.

In 2014, the NTSB recommended that the Federal Aviation Administration impose greater oversight on hot air balloon operators, government documents show.

"The potential for a high number of fatalities in a single air tour balloon accident is of particular concern if air tour balloon operators continue to conduct operations under less stringent regulations and oversight," then-NTSB Chairman Deborah Hersman wrote then. Shepointed to a 2013 commercial balloon tour accident in Egypt that resulted in 19 deaths.

The FAA rejected the recommendations..

Lynn Lunsford with the FAA said in a statement that the accident happened about 7:40 a.m. near Lockhart when the hot air balloon crashed into a pasture. Lockhart is about 30 miles south of Austin.

The site of the crash appears to be directly under large power lines. The land near the crash site is mostly farmland, with corn crops and grazing cattle.

Cutting through that farmland is a row of massive, high-capacity transmission lines, and the site of the crash appears to be right below the overhead lines.

Caldwell County Sheriff’s Office said it received a 911 call about a possible vehicle accident Saturday morning. When authorities arrived on the scene "it was apparent that the reported fire was the basket portion of a hot air balloon," the sheriff's office said.

The names of pilots and passengers have not been released.

Authorities have not said where the balloon was based out of, though Law told the AP that it's the kind of situation where people can walk up and buy a ticket, unlike an airplane, which would have a list of names. 

Lunsford said the FAA is investigating.

Texas Gov. Greg Abbott released a statement on the crash, saying: "Cecilia and I extend our deepest condolences for all those who have been affected by today’s heartbreaking tragedy. Our thoughts and prayers are with the victims and their families, as well as the Lockhart community. The investigation into the cause of this tragic accident will continue, and I ask all of Texas to join us in praying for those lost."