Austin-Travis County EMS tweeted Thursday evening that at least one person was injured but that details about the severity of those injuries and the explosion itself were unknown.
What else do we know of the FedEx explosion?
Chief Michael Hansen of the Schertz Police Department said the explosion was called in about 12:25 a.m. Tuesday.
"The use of a tripwire is far less discriminating than leaving parcel bombs at residences and suggests that (Sunday's) victims were not specifically targeted", the global think tank Stratfor said in one of its Threat Lens reports. "We are very strong".
The fifth bomb went off at a FedEx ground sorting facility, about an hour's drive from Austin.
The blast comes as authorities search for answers to a series of explosions that have rattled Austin. "But it also increases the likelihood that he would make a mistake".
Later, Attorney General Ken Paxton told television station KXAN that the package circulating through the distribution center was sent from Austin and addressed to someone in Austin.
'We are investigating it as being possibly related to our open investigation, ' FBI spokeswoman Michelle Lee told the Austin American-Statesman newspaper.
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The sheriff's office did not immediately respond to a request for comment on whether Zachary Cruz had legal representation. He also told the clinician he owned only a pellet gun and was not capable of doing "serious harm" to anyone.
Authorities roped off a large area around the shopping center in the Austin enclave of Sunset Valley where the store is situated.
"We are working under the belief that this is related to the other bombing incidents that have occurred in our community over the last couple weeks", Interim Austin Police Chief Brian Manley said at a news conference early Monday.
A package bomb exploded shortly after midnight Tuesday inside a FedEx distribution center in Schertz, Texas, and the Federal Bureau of Investigation and ATF are at the scene, spokeswomen for both agencies told The Washington Post. The city's fire department said a hazmat team was there to help with the investigation.
3/15/2018 (morning) AUSTIN: Two white males are seriously injured as they either walk or ride their bikes over a tripwire, police say.
A Reddit user called "austinbomber" created an AMA thread, claiming he is behind the bombings across Austin. Police said they are investigating whether the bombings were hate crimes.
Mr Combs said more than 350 FBI special agents had been drafted in to work on the investigation, calling it an "unprecedented response".
"We're going to be here for a little while", Smith said.
Although the latest blast did not inflict serious harm, it added to the widening fear of more explosions like four previous ones that have already killed two people and badly wounded four others.
Mr Grote said his son, who lives about 100 yards from the blast, heard the explosion and raced outside.
"Successful serial murderers are determined, adaptable and cognisant of their surroundings, which allows them to learn from their mistakes, improve their abilities and implement new tactics to remain steps ahead of those searching for them", said Enzo Yaksic, co-director of Northeastern University's Atypical Homicide Research Group. "We are sending all of the evidence to the ATF lab in Quantico, and they are conducting all of the post-blast analysis of the evidence that we have recovered".