The National Transportation Safety Board and the Federal Aviation Administration were in Lakeland on Friday, investigating Thursday's plane crash.

According to Lakeland police, a Piper Apache A23 crashed into a warehouse used as a chemical storage facility by Key Safety Systems.

Police say 62-year-old Terry Butt, of Winter Haven, and 41-year-old Gregory Geng, of Hudson, were killed in the crash.

Both Butt and Geng attended Tail Wheels Etc., a local flight school based out of Lakeland Linder Regional Airport. It remains unclear who was at the controls of the plane when it crashed.

Officials from the flight school spoke to the public on Friday, but shared very few details about the crash.

"This has been a difficult time for everyone here at Tail Wheels and our family," said Eddie McGuire,Tail Wheels Etc. spokesperson. "We appreciate privacy as we grieve the loss of our co-workers and our friends."

Geng leaves behind his wife and two kids. He owned Admiral Air Cooling & Heating in New Port Richey.  Butt was engaged to be married and had a passion for flying.

Those close to Butt and Geng are patiently waiting for answers while NTSB wraps up its investigation.

The crash, which happened just before 10 a.m., caused a fire at the warehouse and a hazardous materials problem. Firefighters were kept out of the warehouse due to the explosive nature of the chemicals.

The building contains powdered aluminum and nitroguanidine, chemicals used in making airbags. Hazardous materials teams were called in to assist in the cleanup.

There was no one inside of the building at the time of the crash.

The Lakeland Fire Department has been manning the site since the crash due to the explosive nature of the chemicals.

Officials said due to the chemicals and fire, the plane was completely burned.

Debris and human remains were recovered from the site Friday afternoon as well as remains believed to be those of Butt and Geng, 41. The remains will be taken to the Medical Examiner’s office for examination.