The fire department heard a loud explosion. It was a "fireball out of the air," said the mayor.

Four people are dead, including a child, after a helicopter crashed into a radio tower in Houston Sunday night, according to authorities.

"This is a tragic event tonight," Houston Police Chief J. Noe Diaz said at a press conference on Sunday night. "A tragic loss of life."

The helicopter, a Robinson R44, crashed into a radio tower Sunday while it was conducting an air tour flight when it crashed, the National Transportation Safety Board, NTSB, said in a statement emailed to USA TODAY.

Four people were onboard the craft when it crashed, according to the Federal Aviation Administration.

The crash happened at 7:54 p.m. local time, according to a post by the Houston Fire Department on X, formerly known as Twitter.

All four people onboard the craft were killed, said Diaz.

Crash being investigated

The aircraft had taken off from Ellington Airport, according to Houston Mayor John Whitmire. The crash then occurred around 17 miles northwest near North Ennis Street and Engelke Street.

The FAA, NTSB, Houston Police Department, Texas Department of Public Safety and Houston Fire Department are investigating the crash, said Houston Fire Department Chief Thomas Muñoz.

The NTSB will lead the investigation, according to the FAA.

"NTSB investigators are en route to the scene and are expected to arrive later today," the NTSB said in a statement it emailed to USA TODAY. "Once on site, the investigators will begin the process of documenting the scene and examining the aircraft. The aircraft will then be recovered to a secure facility for further evaluation."

The agency will investigate the the pilot, the aircraft and the operating environment and gather the flight track data, weather forecasts, aircraft maintenance records and more.

The NTSB asks anyone with footage or information regarding the crash to submit it to witness@ntsb.gov.

The cause of the crash is still unknown.

"During the on-scene phase of the investigative process, the NTSB does not determine or speculate about the cause of the accident," the agency stated.

USA TODAY reached out to all the agencies involved for more information.

No other structures or homes were damaged in the crash, and the fire caused by the crash was put out.

What we know so far

Multiple fatalities were confirmed by Diaz. Four people are dead, including a minor.

The crash occurred Sunday night at 7:54 p.m.

The helicopter took off from Ellington Airport, its planned destination is unknown.

Chief: Don't touch pieces of aircraft

Diaz asks that people not touch any pieces of the aircraft or shrapnel from the crash and instead call 911 to notify the fire or police departments.

"Let us know where it is if you see it in the community," said Diaz. "It will be a large investigation because of the expanse of the accident."

Large explosion was a 'fireball'

When the crash happened, Houston Fire Department's Station 17 "heard a loud explosion," said Houston Mayor John Whitmire at the press conference. "Immediately, 911 was lighting up."

The explosion was like a "fireball out of the air," said the mayor.

Residents in the area are safe, but the helicopter and tower were "destroyed."

Radio tower lights inoperable days before the crash

The tower's lights were reported as inoperable on October 16, according to KHOU 11.

The story is developing.