The FBI said Tuesday that a package that exploded at a FedEx facility outside San Antonio, Texas, was likely linked to four recent explosions in Austin.

The bomb detonated just after midnight, injuring one employee who was treated at the scene. Police believe the package was headed to Austin, but did not release details about where exactly it was meant to go.

The incident strengthened law enforcement officials’ suspicions, expressed Monday by Austin Police Chief Brian Manley, that “we are clearly dealing with what we expect to be a serial bomber at this point.”

“We suspect it is related to our investigation,” confirmed Michelle Lee, a spokesperson for the FBI’s San Antonio office.