An improvised explosive device was detonated against the exterior wall of a building housing the Colorado Springs chapter of the NAACP on Tuesday, officials said.

The explosion knocked items off the office walls but no one was injured.

Agents from the FBI Joint Terrorism Task Force and the Bureau of Alcohol, Tobacco, Firearms and Explosives went to the scene after the blast to gather evidence and place markers.

The FBI said that a gasoline can was placed next to the device but the contents did not ignite.

According to the the FBI, officials are seeking a “potential person of interest,” described as a balding white male, about 40 years old.

“He may be driving a 2000 or older model dirty, white pick-up truck with paneling, a dark colored bed liner, open tailgate, and a missing or covered license plate,” the FBI said in a statement said.

NAACP president: Organization remains “vigilant” after Colorado Springs blast

The explosion was heard near the building on the 600 block of South El Paso Street on the southern end of the city just before 11 a.m. Those nearby reported hearing a “loud boom.”

“I was cutting somebody’s hair and I heard the explosion,” said Gene Southerland, the owner of Mr. G’s Hair Design Studio in the same building. “It was such a loud explosion that some plastic containers fell off the shelf.”

Henry Allen Jr., the NAACP chapter president, told The Gazette the explosion was strong enough to knock items off the walls and that volunteers who looked outside to see what happened saw what they described as a gas can rigged with some kind of incendiary device, such as a flare.

“We’ll move on,” Allen told the newspaper. “This won’t deter us from doing the job we want to do in the community.”

Photos from the scene showed evidence markers littering the area surrounding the building, local police and their police bomb squad maneuvering around yellow tape.

“The investigation is ongoing and it is not known at this time if the NAACP or a business in the vicinity was the intended target,” said Amy Sanders, an FBI special agent.

Anyone with information about the explosive device should call the FBI tip line at (303) 435-7787

Staff Writer Anthony Cotton contributed to this report.

Jesse Paul: 303-954-1733, jpaul@denverpost.com or twitter.com/JesseAPaul