There was no sign of criminal activity involved in the Beltsville USDA fire, but ATF say the investigation into the cause of the fire continues.

Federal and local investigators were trying to determine if the big, fast-moving fire at the USDA Research Center in Beltsville had anything to do with email threats last week.

Those threats were taken seriously enough to briefly close down the Beltsville facility and five other Agriculture Department facilities around the country.

Investigators still on the scene here in this gutted workshop and storage facility, which was loaded with 55 gallon drums filled with fuel.

They say it's just too early to determine if this fire was accidental or arson.

The blaze ripped through the old wood building in minutes.

Driven by a steady breeze and plenty of flammable materials, the smoke and flames roared into the air and were visible for miles.

Workers at the facility immediately worried that this might not be an accident.

“We're all a little bit on edge,” said maintenance worker Drew Taylor. “But there's been a lot of stepped up security.”

The building is just off Powder Mill Road, which is open to the public to cut through the sprawling Beltsville Agricultural Research Center.

Workers were sent home last week after many of them received an anonymous but threatening emailed message.

“We're aware of the threats that were made, certainly it will be taken into context in the investigation,” said David Cheplak, a special agent and spokesman with the Bureau of Alcohol, Tobacco, Firearms and Explosives, which is investigating. “But at this point, we're not making a statement either way as to whether those threats are related to this event.”

Firefighters say the building was loaded with things that might have accidentally touch off the blaze. Fifty-five gallon drums of gas and diesel fuel, all terrain vehicles and old wiring.

It could take even longer to determine exactly where and how this fire started because of all the damage.

“Just an accident hopefully. Let's think that way,” said Taylor.

The Agricultural Research Center is slated to hold its big, annual public field day on Saturday.

Workers say some of the exhibits for that were stored in this gutted building.

Firefighters say the building house a whole bunch of different workshops.

Ironically, that includes one where workers service fire extinguishers.