An armed maniac lit an “incendiary device” outside a federal government building in lower Manhattan early Monday in an attack being investigated by the terrorism task force, according to officials and sources.

The unidentified man started a fire outside of 26 Federal Plaza around 8:30 a.m., ignited fireworks and threatened passersby with airsoft rifles around 8:30 a.m., police and sources said.

Federal police took the perpetrator into custody at the scene.

“This morning an individual deployed an incendiary device outside of 26 Federal Plaza,” the FBI confirmed to Fox News in a statement.

“The individual has been taken into custody and the FBI New York Joint Terrorism Task Force is investigating the incident.”

The man was pulling a cart containing to long firearms, more fireworks and other items, sources told The Post.

One person suffered minor injuries during the incident and was taken to an area hospital, sources said.