0124 GMT September 20, 2019
The latest explosion took place at a FedEx distribution facility in the town of Schertz near San Antonio.
Quoting FBI agents, The Washington Post reported that the new package had been bound for Austin, the state's capital.
This was the fifth explosion to hit Texas in less than three weeks.
The first blast was a package bomb that exploded at a northeast Austin home on March 2, killing Stephen House, 39. Two more package bombs detonated farther south on March 12, killing 17-year-old Draylen Mason and injuring two women, including his mother.
The fourth explosion rocked southwest Austin on Sunday, sending two men, both in their 20s, to hospital with serious, but non-life-threatening injuries.
Authorities said the first explosions involved packages left overnight on doorsteps. The forth one, however, was triggered by a tripwire.
"With this tripwire, this changes things," said Christopher Combs, special agent in charge of the FBI's San Antonio division. "It's more sophisticated, it's not targeted to individuals ... a child could be walking down a sidewalk and hit something."
Austin Police Chief Brian Manley has asked Texas to remain vigilant and contact authorities upon spotting suspicious, and cautioned against approaching suspicious items, including boxes and bags.
"We are clearly dealing with a serial bomber," Manley said, adding that he was unable to answer questions from reporters about whether the incidents should be considered domestic terrorism. "We will have to determine if we see a specific ideology behind this."
Local and federal authorities have increased the reward for information leading to a conviction in the bombings to $100,000, Manley said. Texas Governor Greg Abbott has also offered $15,000.