A homemade bomb exploded at a FedEx distribution center outside San Antonio on Tuesday, injuring one person in the fifth blast to hit Texas over the past month.
The bomb detonated just after midnight at the FedEx facility in the city of Schertz, northeast of San Antonio.
The package had been bound for Austin, the location of previous deadly blasts.
In a statement on social media, the Schertz Police Department said one person received medical assistance at the scene.
Later on Tuesday, one person was seriously injured in the Texas state capital in an explosion at a Goodwill store, the Austin Police Department said.
Police said an incendiary device exploded, but that it was not related to previous bombings.
A serial bomber?
The most recent blasts follows four other bombs that killed two people and injured six others over the past month.
Last week, officials said they believed the first four bombs were the work of a serial bomber.
"We are investigating it as being possibly related to our open investigation," FBI spokeswoman Michelle Lee told the Austin American-Statesman newspaper.
"We can't know for sure until we have an opportunity to look at the evidence itself," she added.
The Tuesday blast comes after an explosion on Sunday night that was triggered on a street by an almost invisible tripwire, suggesting a "higher level of sophistication" than agents had seen in previous bombings.
The three earlier incidents involved package bombs that were left on doorsteps, meaning officials now believe the bombings have been done at random, rather than being targeted at someone in particular.
Potential hate crimes
Austin police chief Brian Manley said police have not been able to determine a motive for the bombings, but police had looked at the possibility of hate crimes.
The first two bombs killed black men and investigators believed the third, which left a Latina woman injured, may have been intended for a black family's home, police said.
cw, law/se (AFP, AP, dpa, Reuters)