Authorities gave two explanations for an explosion near the Minnesota State Capitol this afternoon, a day before the start of the Republican National Convention: It was a test. Or, it was an accident.

Minnesota State Patrol spokesman Mark Peterson said a "response team" set off a "flash bang grenade" in the State Office Building parking ramp about noon. The device makes a loud noise, and is used by authorities upon entering a building to surprise occupants.

Peterson would not say what agency was testing the device. When asked why the testing was occurring a day before the RNC, Peterson said, "I don't have that information for you."

When asked if such tests would occur regularly throughout the RNC, he said, "Haven't got that for you right now."

St. Paul police spokesman Peter Panos said a State Patrol employee accidentally dropped his flash bang grenade near Rice Street and Aurora Avenue.

"It just accidentally went off," Panos said. "All it does is make a big noise."

It's unclear how the accident occurred.