A package bomb that authorities believe is linked to the recent string of Austin bombings exploded early Tuesday inside of a FedEx distribution center near San Antonio, leaving one worker with minor injuries.

The explosion happened at around 1:00 a.m. at a FedEx facility in Schertz, which is just northeast of San Antonio, FBI Special Agent Michelle Lee said. One worker was treated for minor injuries and released, according to statements issued by the Schertz Police Department and FedEx.

Lee said that although it is still early in the investigation, "it would be silly for us not to admit that we suspect it's related" to the four Austin bombings that have killed two people and injured four others since March 2. She didn't have details about the size, weight or description of the package.

The most recent bombing in Austin injured two men Sunday night in the quiet neighborhood of Travis Country in the southeast of the city. It was triggered along a street by a nearly invisible tripwire, suggesting a "higher level of sophistication" than agents saw in three early package bombs left on doorsteps, according to Fred Milanowski, agent in charge of the Houston division of the federal Bureau of Alcohol, Tobacco, Firearms and Explosives.

Sunday's attack means the carnage by a suspected serial bomber that has terrorized Austin for weeks is now random, rather than targeted at someone in particular.

Authorities repeated prior warnings about not touching unexpected packages and also issued new ones to be wary of any stray object left in public, especially ones with protruding wires.

Local and state police and hundreds of federal agents are investigating, and the reward for information leading to an arrest has climbed to $115,000.

"We are clearly dealing with what we believe to be a serial bomber at this point," Austin police Chief Brian Manley said, citing similarities among the four bombs. He would not elaborate, though, saying he didn't want to undermine the investigation.

It is not yet clear if the explosion at a FedEx facility Tuesday morning is at all connected with the bombings in Austin.