An explosion has taken place at a mail facility near San Antonio, Texas just two days after a bomb went off in Austin, Texas -- the fourth such bombing in the city this month.

According to Schertz police, the explosion took place at a FedEx distribution facility in Schertz, Texas, just after midnight on Tuesday. Schertz is about 65 miles southwest of Austin.

According to police, who spoke with San Antonio ABC affiliate KSAT, a medium-sized box exploded at the facility.

One worker possibly suffered minor injuries in the explosion. They were not taken to the hospital, the official said. There were 75 people in the building at the time of the explosion.

Police said they "hope" this is an isolated incident and do not yet know if it is connected to the Austin bombings.

Austin has been on edge for a month after a series of bombings which killed two and injured four people. The first three bombings were packages, apparently hand delivered police said, that exploded after being picked up by residents at the homes.

The fourth explosion took place Sunday night. Two men in their 20s were injured in that explosion, which was caused by a device using a trip wire on a sidewalk in the city's Travis Country neighborhood.