Federal officials are investigating a Delta Air Lines flight that taxied around the Las Vegas airport for nearly 90 minutes on Monday in triple-digit temperatures, causing at least one person to need medical treatment.

"The reports are shocking and we are investigating," said Transportation Secretary Pete Buttigieg, who spoke in an interview with Reuters, which was confirmed to CNN by a transportation department official.

"I want to know how it was possible for passengers to be left in triple-digit heat onboard an aircraft for that long," he said.

An official told CNN the transportation department "will hold the airline accountable for any violations," including of rules around how long airplanes may sit on the ground with passengers aboard.

Federal rules say the major US airlines must allow passengers to get off if a delay lasts three hours or longer for domestic flights. For international flights, the threshold is four hours. Airlines must provide a snack and water if a delay lasts longer than two hours.

Delta said it is aware of and cooperating with the investigation.

The airline has apologized for the incident and said at least one person required medical attention "for heat-related discomfort."

They are also "looking into the circumstances that led to uncomfortable temperatures inside the cabin."

The airplane tracking website FlightRadar24 shows the Boeing 757 aircraft left a gate at the Las Vegas airport on Monday afternoon but never left the ground. The plane taxied to the end of a runway and then turned around and returned to the terminal.

The loop took at least 86 minutes, according to FlightRadar24 data.

Airlines can face significant fines for violations of the delay regulations. In 2019, Delta received a $750,000 fine for 11 flights that violated the rule. The airline was given credit toward that fine for spending $450,000 on customer compensation and upgrading technology and processes.