LINO LAKES, Minn. -- Two people died when a helicopter erupted in “a large fireball” as it crashed into a field in a Twin Cities suburb, a sheriff’s official said Friday.

The aircraft crashed near a residential area in Lino Lakes about 5:30 p.m. Thursday, Anoka County Sheriff’s Cmdr. Paul Sommer said from the scene late Thursday.

“We can’t identify much based on what remains in the field. It’s basically charred up debris,” Sommer said. “This is a horrible tragedy. I can’t begin to describe what that scene looks like.”

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“There’s a large fireball and there’s wreckage,” he said.

Sommer tweeted Friday that two people died in the crash. No one on the ground was hurt.

Sommer described conflicting witness accounts of what happened to the helicopter before it crashed. Some witnesses reported seeing the helicopter’s blade stop turning before it “dropped out of the sky,” he said. Others told authorities that the helicopter began to break up before hitting the ground and bursting into flames.

Witness Eddie Turner told CBS Station WCCO he saw something fall from the helicopter while it was still airborne. “And then when it hit the ground, there was a huge fireball.”

Sommer said it didn’t appear that the crash was caused by an entanglement with power lines, saying the helicopter was flying at a much higher altitude when it started to go down.

The Federal Aviation Administration and National Transportation Safety Board will investigate, according to FAA spokeswoman Elizabeth Isham Cory. Authorities asked Lino Lakes residents to contact the police if they find any objects that could be debris from the aircraft.

Lino Lakes is about 17 miles north of downtown St. Paul.