SCHERTZ, Texas -- A box exploded in the sorting area of a FedEx ground facility in Schertz, Texas, about 30 minutes northeast of San Antonio, police say.
At 12:30 a.m. Tuesday, authorities responded after receiving a call about an explosion at the building where 75 people were inside at the time.
Officials say a FedEx employee was injured from the sound of the explosion. She apparently suffered a non-life threatening "percussion-type" injury from the blast.
She was treated and released at the scene.
Investigators are checking on employees to make sure they're OK. They're also taking statements from them about the incident.
No word where the package was headed or what was inside of it.
The FBI and ATF are at the scene.
A law enforcement source tells ABC News authorities will have to move slowly and methodically to process the complex scene where other FedEx packages containing unknown contents are all over the facility.
Officials are calling this "a complicated and potentially dangerous environment to render safe."
FedEx released a statement about the explosion, saying:
"We can confirm that a single package exploded while in a FedEx Ground sortation facility early this morning. One team member is being treated for minor injuries. We are working closely with law enforcement in their investigation. We are not providing any additional specific information about this package at this time."
This comes after Austin was rocked with the fourth explosion to hit the city in just two weeks.
Federal agents say this package is likely linked to attacks by what they believe is a serial bomber.
Police are urging anyone who sees something suspicious to report it.
The Associated Press contributed to this report.
1 person injured after box explodes at FedEx facility near San Antonio