DENVER (AP) — Staff members at a Colorado NAACP office say they are waiting for more information before drawing any conclusions about an explosion near their chapter, even as the FBI said it was investigating whether it was a case of domestic terrorism.

"We're standing vigilant and are trying not to let this disrupt anything," Colorado Springs NAACP volunteer Harry Leroy said Wednesday, a day after someone set off a homemade explosive device outside the group's building, about an hour south of Denver.

The FBI said it is investigating the possibility that the act was a case of domestic terrorism, but it had not determined whether the nation's oldest civil rights organization was targeted.

"We're exploring any potential motive, and domestic terrorism is certainly one among many possibilities," Denver FBI spokeswoman Amy Sanders said.

The blast happened about 11 a.m. Tuesday outside a barbershop that shares a building with the NAACP chapter. There were no injuries and only minor damage.

While local chapter members said they were not making any conclusions, speculation washed across social media about whether the explosion was a hate crime. Investigators have not ruled out any possibilities, Sanders said.

An improvised explosive device was detonated against the low-slung building, which sits in a mostly residential neighborhood, but a gasoline canister placed next to the device failed to ignite. Members of the FBI's Joint Terrorism Task Force are investigating because of the explosion's proximity to the NAACP office, Sanders said.

Investigators were still looking for a balding white man in his 40s who might be driving a dirty pickup truck. His identity was still under investigation.

"This is someone we'd like to speak to," Sanders said.

Republican Sen. Kent Lambert, whose district includes the NAACP office, said such violence will not be tolerated.

"We will track you down, prosecute you to the fullest extent of the law and put you in prison," he said. "We will not tolerate that kind of violence in our society."

Both the chapter office and the barbershop reopened Wednesday with little police presence.

Investigators were briefing the chapter's president, Henry Allen Jr., and he did not return calls seeking for comment.

"We'll move on," Allen wrote on the chapter's Facebook page. "This won't deter us from doing the job we want to do in the community."

Gene Southerland owns Mr. G's Hair Design Studios next door and was cutting a client's hair there when the explosion occurred. The blast was strong enough to knock items off the walls, but the quick police response was comforting, he said.

Southerland said the FBI had given him no information on its early findings. But he said he didn't believe the barbershop or its predominantly black clientele was targeted.

Leroy said he believed there were surveillance cameras behind the building, but he did not know whether they captured anything of value.

Gregory Alan Johnson, who lives nearby, said he was unaware of any prior problems near the NAACP offices. Colorado Springs police wouldn't comment about the case, but Lt. Catherine Buckley said the department found nothing concerning in any previous calls for service.

Those who heard the blast, including Southerland, said it sounded like a single, loud "boom."

Investigators Tuesday were examining a red gasoline canister with a yellow nozzle. They also checked pieces of duct tape and metal lying 40 to 50 feet from the explosion site.

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(Photo: AP Photo/The Colorado Springs Gazette, Mark Reis)