The devices went off Friday and two others were disarmed at the homes of a Federal Aviation Administration employee and workers at Serco Group Pcl., which operates 56 air traffic control towers. No one was hurt and damage was minor.
An improvised explosive device was detonated on the roof of the Serco project management office in Murfreesboro, Tenn., on Feb. 1, said Kenny Spann of the Bureau of Alcohol, Tobacco, Firearms and Explosives. No one was hurt.
"There are strong similarities between the components and design of these devices," Spann said.
Police have described the bombs as containers resembling office-style trash cans with a device strapped to them.
Security at Serco's towers was increased since the explosions, said Pete Dumont, Serco's vice president for aviation.
Federal investigators have obtained an arrest warrant for Robert L. Burke, 54, a former Serco employee who was fired two years ago while working as an air traffic controller at Walker Field in Grand Junction.
Burke, who worked for Serco for 10 years, also uses the name Robert Pope, Spann said.
Dumont said Burke had worked in Salinas, Calif., and Mesa and Flagstaff, Ariz., but couldn't comment on Burke's record because of confidentiality laws.