A homemade bomb exploded outside the offices of the Colorado Springs chapter of the NAACP civil rights group on Tuesday, authorities said, but a gasoline can placed next to the device failed to detonate and no injuries were reported.

An “improvised explosive device” was set off against an exterior wall of the NAACP building, the FBI’s Denver field office said in a statement.

“A gasoline can had been placed adjacent to the device, however, the contents of the can did not ignite upon explosion,” the statement said.

The FBI did not say whether the country’s oldest civil rights organization was specifically targeted or if race played a role in the incident.

A woman who answered the phone at the NAACP office but declined to give her name said people inside the building heard a “loud boom” coming from a lawn area in the rear.

The blast, which occurred about 70 miles south of Denver, caused “only minimal surface charring” to the building, which also houses a hair salon, authorities said.

The FBI and Colorado Springs police are investigating the incident and are looking for a person of interest who is described as a balding Caucasian man about 40 years old who may be driving a pickup truck, the statement said.