A parcel bomb has exploded at a FedEx depot near San Antonio, Texas, injuring one.
The incident reportedly occurred overnight in the town of Schertz, an hour south of Austin where four bombs have been planted in recent weeks.
The Washington Post reported that police were investigating possible links to the previous devices, which killed two people.
Authorities believe the previous blasts are the work of a serial bomber.
According to BBC, three of the four previous devices planted in Austin were hidden in parcels left at residential addresses. Police said another was probably activated by a tripwire, triggered by two men walking along a street in south-west Austin.
The first exploded on 2 March, killing Anthony Stephan House, 29, at his home.
Two more bombs exploded 10 days later. Draylen William Mason, 17, was killed and his mother was critically injured when he brought a package inside his home.
Hours later, a 75-year-old Hispanic woman, who has not been named, was injured by another package.