Barely an hour after the Austin Police Department announced two separate deadly package explosions were linked, a third explosion was reported at an Austin home.

This time, the victim survived the blast but still suffered life-threatening injuries. She has only been identified as an elderly woman in her 70s.

The latest explosion to rock the Texas capital came five hours after an explosion in a quiet east Austin neighborhood killed a teen boy and injured a woman in her 40s. Police said it shares similarities with that detonation and a fatal blast at a home in north Austin March 2.

In the all of the blasts, the explosive was encased in a package that was left on the front porch. None was delivered by mail services.

The victims in the first two blasts were black; the third, Hispanic. Police say racial motivation is being considered as a possible motive, but all other possibilities are being considered as well.

According to Austin police, Monday began with an "urgent" 911 call just before 6:45 a.m. local time at a home in Austin's Windsor Park neighborhood.

"Upon arrival ... what we found was an explosion had occurred inside the residence. There were two people that had been injured," a police department spokesperson said.

The surviving woman's injuries are potentially life-threatening, according to CBS Austin. The teen, identified only as a male around 17, died at the scene.

Neighbors were evacuated to a city bus that had been on its morning route in the area. Bomb-sniffing dogs went from home to home checking for any other explosives. None were uncovered.

Police say the second call of the day Monday came at 11:50 a.m. CST at a home in southeast Austin, 5 miles away from the first call.

The March 2 incident happened in southeast Austin 12 miles from the first blast Monday and 16 miles from the second. A 39-year-old man was killed.

As law enforcement work to find the culprit, they are warning the public to be vigilant about any suspicious-looking or unexpected packages.

"I want the public to be aware and to be cautious because we have two cases very similar with both resulting in loss of life... If you receive a package not marked appropriately or from someone you know or were not expecting, give us a call," the spokesperson said.

CBS Austin reports Austin police took more than 150 suspicious package calls Monday following the two explosions.

The FBI and ATF are assisting the Austin Police Department in the investigation.