AUSTIN, Texas – A small plane crashed Thursday into a multistory office building in Austin, causing a fire and sending black smoke billowing from the seven-story structure, officials said. At least two people were injured and a third was unaccounted for.

Law enforcement officials in Austin said the pilot may have intentionally crashed the plane.

The aircraft hit the Echelon Building, which is next to a major highway in north Austin.

Fires were burning from the second through fourth floors, KXAN reported. Crews used ladder trucks and hoses to battle the blazes. Dozens of windows were blown out of the hulking black building and vehicles traveling on a nearby highway paused to look.

Authorities were conducting a roll call to try to account for all the workers who were in the building.

Two people were taken to a hospital, Austin Assistant Fire Chief Harry Evans said. The nature and severity of their injuries wasn’t immediately clear. A third person was unaccounted for, Evans said.

It was not immediately known where the plane was headed. The nearest airport is Austin Bergstrom International Airport, which is some 15 miles away.

Authorities were investigating whether the plane crash was related to an Austin house fire earlier in the day.

Emergency crews were called to a one-alarm fire at a residence. There were no injuries but authorities were investigating whether the blaze was intentionally set.

The IRS, CIA and FBI all have offices in the complex where the building is located, though it was not clear if they are in the building that was hit. The FBI said its office was not in the building that was struck.

“At this time we have no reason to believe there is a nexus to criminal or terrorist activity,” said Department of Homeland Security Deputy Press Secretary Matt Chandler.

FBI sources told the Austin Statesman-American that several eyewitness accounts saying that the plane did not slow down is making some authorities wonder if it was an intentional act.