The first blast, reported about 6:44 a.m., killed a male teenager and injured a woman in her 40s. The second explosion today injured another woman, with authorities evaluating whether a second person was also hurt, according to the Austin Police Department.
Police Chief Brian Manley said today that today's two explosions are linked to a March 2 blast in Austin, though there is "no specific ideology or victimology behind this."
Investigators said earlier that first blast today might be connected to a March 2 blast in Austin because of the composition of the explosive device used. The police chief declined to discuss the construction of the explosive device or what specific elements make it look similar to the earlier one.
The explosion "is very similar to the incident that occurred in Austin back on March 2, and if you'll remember, that incident also occurred in the morning hours when the victim, in that case, went out front and found a package on their front steps that exploded causing that individual's death," Manley said at a news conference Monday.
What is known about today's blastsThe first explosion today occurred at a single-family house in the northeast section of the city and appears to have been caused by a package that had been placed on the porch of a home rather than delivered by a mail service, police said. Police believe the explosion happened after residents took the package inside to open it.
"What we understand at this point is that earlier this morning, residents went out front, and there was a package on the front doorstep. They brought that package inside the residence and as they opened that package, both victims were in the kitchen and the package exploded causing the injuries that resulted in the young man's death and the injuries to the adult female," Manley said today.
The Austin police received calls about today's second blast at 11:50 a.m. and the victim is a 75-year-old Hispanic female.
"The victim in this incident came outside of her residence and found a package out front and picked up that package," Manley said, noting that the woman, whose name has not been released, was "significantly injured" and is currently listed in critical condition but stable.
Dianna DeLafuente said that she heard today's second blast at a neighbor's house.
"We were all just inside the house and we heard the explosion," she told ABC News.
An explosion earlier this monthToday's blasts follow the explosion on March 2, which police received a call about at 6:55 a.m. that day.
The victim in that explosion, Anthony Stephan House, died from his injuries after being transported to a local hospital.
"That case was being investigated as a suspicious death," Manley said today. "It is now being reclassified and is now a homicide investigation as well. We are looking at these incidents as being related based on similarities that we have seen and the initial evidence that we have on hand here today compared to what we found on the scene of that explosion that took place a week back."
Manley noted that "we don't know the motive behind these" events though he said that two of the three homes involved in blasts today and on March 2 had African-American residents. The victim in the third blast, which was called in just before noon today, was an elderly Hispanic woman.
"We can not rule [out] that hate crime is at the core of this, but we're not saying that's the cause as well," he said.
Looking at the packagesAuthorities have warned residents that if they receive a package they are not expecting, they should contact the Austin Police Department.
Manley said that the packages involved so far have been "box-type deliveries" and they "have all occurred at residences and we don't want people to be overly alarmed but it is important that people be vigilant."
"We do not believe this was delivered by any official delivery service," Manley said, specifically citing the U.S. Postal Service, UPS, DHL or others.
Manley said that these are "very powerful devices" and they caused "significant" damage to the houses involved in both the March 2 blast as well as the first explosion this morning.
The FBI told ABC News that it was responding to the first reported explosion and assisting Austin police, who are the lead agency handling the situation.
The Bureau of Alcohol, Tobacco, Firearms and Explosives has sent staff from both its national response team and reinforcements to bolster local field resources. The national response team is the entity that goes into major incidents to investigate complex fires and explosions -- most recently the church fires in the south and the Oakland warehouse catastrophe.
Today's blasts come at a particularly busy time for Austin, as the city hosts the annual SXSW music, film and technology conference from March 13 until March 18.
Texas Gov. Greg Abbott has issued a $15,000 award for information that leads to the arrest of the person or persons involved with the blasts.
"I want to assure all Texans, and especially those in Austin, that local, state and federal law enforcement officials are working diligently to find those responsible for these heinous crimes," Abbott said in a statement announcing the reward.
ABC News' Gina Sunseri contributed to this report.