Photographs show the doors of the center bent and burned. Witnesses said someone on a red motorcycle tossed a backpack, which then exploded, Tulsa news station KJRH-TV reported.

The Bixby Police Department said the investigation had been turned over to the federal authorities because the explosion occurred at a military office.

Mandy Vavrinak, a spokeswoman for the Bixby police, said the explosion occurred in a largely commercial and retail area near the border of Tulsa and Bixby, which she described as an “affluent suburban community.”

Even in the Tulsa metropolitan area as a whole, “this is not a common occurrence,” she said. “We don’t have a lot of incidents where the F.B.I. has to come investigate.”

Meredith Davis, a public information officer with the Bureau of Alcohol, Tobacco, Firearms and Explosives, said that it was too early to say whether the center was a target of domestic terrorism, but added that “anytime a military office, installation, or any representation thereof is targeted, you always have to keep that in the back of your mind.”