(CNN) Austin, Texas has been on edge after a string of package bomb explosions -- but a possible blast reported Tuesday night turned out to be unrelated, police say.

The latest incident turned out to be a Goodwill worker who was injured by simulated military ordnance in a donation box.

The worker's injuries were not life-threatening and he was treated and released from a hospital, officials said.

Earlier, authorities said they were responding to a report of a possible explosion, setting off fears a serial bomber had struck again in the Texas capital.

The Goodwill employee found two artillery simulators in a box of dropped-off items, and was injured when one of the ordnances "initiated," Assistant Chief of Austin Police Ely Reyes told reporters.

"This incident is not related to any of the other incidents that we've had here in Austin," Reyes said at a late-night news conference. He added that it didn't appear a copycat was responsible for the Goodwill box.

#UPDATE: There was no package explosion in the 9800 block of Brodie Ln. Items inside package was not a bomb, rather an incendiary device. At this time, we have no reason to believe this incident is related to previous package bombs. #Breaking #packagebombmurders — Austin Police Dept (@Austin_Police) March 21, 2018

The news of the incident came on a day two packages, one in a different part of Texas, caused authorities to widen their investigation.

The two packages, one that exploded at a FedEx sorting center near San Antonio and another later discovered back in Austin, are connected to four bombings in Austin, law enforcement agencies said Tuesday evening.

The ATF tweeted Tuesday evening that it, the FBI and Austin police had confirmed the connection.

One package Tuesday injured a FedEx worker in Schertz, near San Antonio, when the parcel went off just after midnight, officials said. Schertz is a little more than an hour southwest of Austin.

A second package, which was found at a FedEx facility near Austin's international airport, was being examined by authorities, the FBI's San Antonio office said in a tweet Tuesday afternoon.

Tuesday's developments added to the anxiety in the state capital, where four package bombs that caused two deaths and reports of other dubious parcels have Austin in what one US lawmaker from Texas described as "absolute panic."

Key developments

• A FedEx spokesman, Jim McCluskey, said of the person who sent the package that exploded Tuesday, "The individual responsible also shipped a second package that has now been secured and turned over to law enforcement."

• The company also gave law enforcement "extensive evidence related to these packages and the individual that shipped them collected from our advanced technology security systems," McCluskey added in a statement.

An ATF vehicle sits at a FedEx sorting center where a package exploded Tuesday in Schertz, Texas.

• The FBI is investigating a "confirmed link" between packages involved in the Austin investigations and a mail delivery office in Sunset Valley, southwest of downtown Austin, police in Sunset Valley said Tuesday. They did not indicate which packages were connected to the Sunset Valley office.

• The FedEx explosion represents a new method for the bomber or bombers. None of the four previous explosives was shipped, police have said.

• Schertz Police Chief Michael Hansen said he was confident the package that exploded there was not meant to target that facility or the city, though he wouldn't say why.

• FBI Special Agent James Smith declined to answer reporters' questions about whether the package that blew up was destined for Austin. Smith also said he had no reason to believe people in Schertz face any threat.

• There have been more than 1,200 calls about suspicious packages that have come in since March 12, Austin police said

• Rep. Sheila Jackson Lee asked an FBI acting deputy director for a briefing in Washington on efforts to find the bomb maker. "There is absolute panic in Austin," said Jackson-Lee, who represents Houston.

• President Donald Trump did not comment when asked Tuesday if he thought the bombings were acts of domestic terrorism. Trump called the situation "absolutely disgraceful" and said of those responsible: "We have to find them really immediately."

The four Austin bombings

In Austin, authorities have been combing for clues to the four explosions there, the first three of which involved cardboard packages left in front yards or on porches. They weren't delivered by the US Postal Service or services such as UPS or FedEx, police say.

Those three explosions -- one on March 2 and two more on March 12 -- killed or wounded three African-American people and one Hispanic person. The blasts happened in east Austin areas that predominantly have minority residents, and some in the area expressed concern the attacks might have been racially motivated

Police have not uncovered a motive and have not ruled out the possibility those bombings could be hate crimes.

In the fourth blast, a device Sunday was triggered by a tripwire, injuring two white men, police said. It had been left on the side of a road in a predominantly white area. Those men are in good condition at St. David's South Austin Medical Center, a hospital representative said.

"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.

At the Schertz FedEx facility, a package that was moving along an automated conveyor exploded around 12:25 a.m. Tuesday, Hansen said. A worker standing near the explosion suffered minor injuries and was treated and released, officials said.

If one perpetrator is behind all five blasts, then the person deployed an unusually wide range of skills and delivery methods, CNN law enforcement analyst James Gagliano said.

"Some of these folks ... as long as the bomb maker walks away with 10 fingers and 10 toes, that's successful to them," said Gagliano, a retired FBI supervisory special agent.

"But the method, the delivery system and the different means that he's having these things in place shows that he's trying to show -- if it's the same person on all five of these -- a full panoply of different ways of doing this," he added, "and that's frightening."

Three members of the Congressional Black Caucus called Monday for federal officials to classify the bombings as terrorist attacks and determine whether they are "ideologically or racially motivated."

'I was pretty scared'

Brian Jaimes, 19, a package handler at the FedEx facility near Austin where investigators were working on a suspicious package, said employees were called to the front office and then told to leave the building.

"I was pretty scared," said Jaimes, who has worked at the facility for four months.

When asked whether the news about the bombings has made him nervous about coming to work, he said: "I try not to think about it, especially since I work (at a package shipper)."

What agencies are involved?

More than 350 special agents assigned by the FBI, as well as Bureau of Alcohol, Tobacco, Firearms and Explosives agents and forensic investigators in Quantico, Virginia, are on the Austin case.

At the state level, about 100 Texas Department of Public Safety officers, sergeants and special agents as well as the Texas Ranger bomb squad, bomb-sniffing dogs, intelligence agents and helicopters are also involved, CNN affiliate KXAN reported.

Police departments in Houston and San Antonio are sending bomb technicians and canine teams to Austin, their police chiefs said Monday.

How are they examining the evidence?

ATF has taken evidence from the four blast sites in Austin, Police Chief Brian Manley said.

"The prior three scenes are already in the lab at Quantico, and the evidence from the scene from last night is on its way to Quantico as well," he told CNN's Anderson Cooper on Monday night.

"They're looking at the devices, they're comparing them, looking for similarities," he said. "The similarities they've seen to this point, lead them to believe -- as we do -- that these are all being constructed by the same person or persons who are responsible for this."

How are officials handling the tips?

Austin police have received lots of tips, Manley said Monday night.

"As each tip comes in, it gets assigned to either a team of FBI agents, ATF agents or Austin police detectives to do follow-up work on," he said.

Manley urged residents to call police with any information.

"No matter how inconsequential you think it may be, that may be the piece of evidence we need to link it together and solve this before we have someone else in our community that gets seriously injured or killed," he said.

What are police asking residents to do?

Police are appealing to residents to pay attention to their surroundings. Residents shouldn't approach or touch anything that looks suspicious, Manley said.

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"We now need the community to have an extra level of vigilance and pay attention to any suspicious device -- whether it be a package or a bag, a backpack -- anything that looks out of place," he said Monday. "Do not approach items like that."