Officials did not say if the latest incident was the work of what Austin police believe could be a serial bomber responsible for the four earlier devices that killed two people and injured four others.
The blast at the FedEx facility in Schertz was the fifth in the state in the last 18 days. If it is linked to the others, it would be the first outside the Austin area and the first that involves a commercial parcel service.
Police discovered another package at the same location that they believe is also loaded with an explosive device, San Antonio Police Chief Bill McManus told reporters.