Agents from the Bureau of Alcohol, Tobacco, Firearms and Explosives are also investigating.
Special Agent Jessi Rice said Tuesday that the blast in the Tulsa suburb of Bixby is not being called terrorism because investigators have not determined a motive and have not identified a suspect.
According to police for the city of Bixby, the explosive device in question was detonated at 10:30 p.m. Monday evening.
Authorities are investigating into what may have caused an explosion next to a Bixby, Oklahoma, U.S. Air Force recruiting office.
Rice said they have a few leads but have not confirmed a suspect yet.
"At this point, we don't know if it was a disgruntled employee, an act of domestic terrorism, just someone playing games".
The FBI is checking with nearby businesses for video, interviewing witnesses and trying to rebuild the bomb. No injuries have been reported.
"Officials said that the explosion occurred near the office at 10:30".
She says agents are treating the explosion late Monday as a possible act of domestic terrorism out of "an abundance of caution", because of its proximity to the recruiting office. The individual or individuals involved in the incident vandalized the building and slashed tires of vehicles at the center.
It is noted that Federal Bureau of Investigation and ATF are investigating the cause of the explosion.