Last week, six USDA offices in five states were shut down because of anonymous emailed threats. This morning, fire gutted a large shed at one of those complexes, USDA’s GMO-focused facility in Beltsville, Md. The Bureau of Alcohol, Tobacco, Firearms and Explosives, which is investigating the blaze, said there was no sign of criminal activity at the site but an investigation into the cause continues.

USDA_logoThe fire took about two hours to extinguish and was located in a facility variously described as a “shed,” a “garage,” and a “workshop and storage facility.” The building contained 55-gallon drums filled with fuel, according to a Washington, DC, television station. Although investigators stress that it is too early to tell if the fire was an accident or arson, WUSA-9 talked to workers who were concerned about the blaze nonetheless.

“We’re all a little bit on edge,” maintenance worker Drew Taylor told the TV station. “But there’s been a lot of stepped up security.”

Workers were sent home last week after many of them received a threatening email. Last week’s threats were taken seriously enough that the FBI visited offices around the country with bomb-sniffing dogs, according to one Denver news source.

Faculty members at North Carolina State, Virginia Tech and the College of William and Mary also received the identical emailed threat. Virginia Tech’s student newspaper, the Collegiate Times, reported that at least four separate accounts received emails with “Warning” as the subject line. The sender used at least four names, including Rex King, Robert Birdman, Jack Bauer, and John Grind.

The email, which was determined to come from outside the U.S., said: “I am here to inform [sic] that in the next couple of days I will break into the campus and will kill as many people as I can until the police arrives [sic].”

Scientists at the Beltsville site research poultry diseases, soybean genetics and genetic modification of food animals, according to its website.