Investigators believe a package caused a small explosion Friday at the Fort Gibson post office.
No one was hurt, and investigators believe it was an isolated incident, but they did evacuate the post office.
Jordann Pollard was sitting nearby, waiting to walk to work, when she said she thought she felt an earthquake.
"My back was up against the wall and I could feel it from outside. It sounded like an earthquake or that something exploded," she said.
It wasn’t an earthquake, but a package that exploded inside the post office.
No one was hurt, but there was some minor damage inside the building.
Post office workers evacuated the building and waited for police and the Post Master’s Office to investigate.
"We don't speculate on that stuff, we let the investigation be the investigation, and at this time we don't have any alarming concerns right now that are pushing us in any particular direction," said Sergeant Michael Roberts with Fort Gibson Police.
Roberts said the Oklahoma Highway Patrol bomb squad was called out and other crews were on standby.
After about an hour, people were able to go inside and get their mail, but the main office was locked and taped off.
"It's just natural protocol we go through because we treat this as a serious event every time and then we can always scale that down, it's just more difficult to scale it back up," Roberts said.
Even though police said there is nothing to worry about, something like this is sure to get the public's attention.
"This day in time, you never know what you are going to come across," Pollard said.
The PIO for the post office confirmed that it was not a bomb and the office will reopen Saturday.