GREENWOOD VILLAGE, Colo. (AP) — Two people died when a small plane crashed and caught on fire in an industrial office park in suburban Denver on Friday, officials said.

The crash happened as the plane was returning to the airport, the National Transportation Safety Board said. Air traffic control audio indicates the pilot had recently taken off and suggests he was circling back to the airport because he was practicing landing and taking off.

The crash was initially reported as an explosion, Deborah Takahara, a spokesperson for the Douglas County Sheriff's Office, said.

Firefighters found the Beech BE35 airplane engulfed in flames, with the fire threatening to spread to a nearby building and some diesel-powered generators, Brian Willie, a spokesperson for South Metro Fire Rescue, said. Firefighters were able to put out the flames, he said.

The plane crashed in a driveway between a warehouse-type building and the generators, Takahara said. It was in a complex that houses data centers serving a variety of companies, according to property records.

Air traffic control audio posted by LiveATC.net includes the pilot telling the tower he planned to do stop-and-gos, which are commonly done to practice landing and taking off. The audio also shows that an air traffic controller cleared the plane for takeoff shortly before the crash.

Another pilot later reported seeing smoke.

“Tower, there’s smoke off the left side. Looks like he went down,” came the report on the audio, followed a few seconds later by: “He appears to have crashed in the parking lot about a mile southeast of the field.”

The NTSB said it will issue a preliminary report on the crash within 30 days. It is investigating the crash along with the Federal Aviation Administration.