Updated at 5:12 p.m. ET

Within a span of several hours Monday morning, two package bombs detonated in separate areas of Austin, Texas, badly injuring the residents who sought to open them and calling to mind a similar blast that killed one person less than two weeks ago. Authorities say there are marked similarities between the three explosions.

"Based on evidence that we have at this scene, as well as the other two scenes where we've had these explosions, this evidence makes us believe that these incidents are related," interim Austin Police Chief Brian Manley told reporters at the site of the third explosion.

"We are putting together a task force that will work jointly until we conclude this investigation and we arrest the person or persons responsible," Manley added. "And we will leave no stone unturned because we are not going to allow this to go on in our city."

A teenager was killed and a woman was injured when a package exploded at a home near Martin Luther King Boulevard and Springdale before 7 a.m. Monday. A few hours later, a 75-year-old woman was taken to the hospital with potentially life-threatening injuries after an explosion in the Montopolis neighborhood.

Less than two weeks ago, a package also exploded and killed 39-year-old Anthony Stephan House at his home.

The FBI and agents with the Bureau of Alcohol, Tobacco, Firearms and Explosives are helping the Austin Police Department investigate.

"We are looking at these [first two] incidents as being related based on similarities that we have seen in the initial evidence," Manley said at a news conference.

Manley said the first two packages were sent to homes of black residents, "so we cannot rule out that hate crime is at the core of this."

The packages were not sent through the U.S. Postal Service, he said; authorities believe they were left on the doorsteps during the night. Manley warned residents not to open any suspicious packages and instead to call 911.

"Until we find who committed this act and take them into custody," he said, "then, yes, it is appropriate for residents to be concerned."

"First and foremost, Cecilia and I offer our thoughts and prayers to the victims of these atrocious attacks," Gov. Greg Abbott said in a statement. "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."

His office is offering a $15,000 reward for information leading to the identification and arrest of anyone involved in the blasts.

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