March 12 (UPI) -- Police in Austin, Texas, said Monday three deadly explosions that targeted three homes this month may be related -- and warned residents to be cautious of suspicious packages left on their doorsteps.
A 75-year-old woman was injured by a third explosion after she walked outside her home in southeast Austin and found a package at 11:50 a.m. Monday.
She was in critical, but stable condition with life-threatening injuries following the blast.
Earlier a 17-year-old boy was killed and a woman was injured after a package exploded at their East Austin home.
A similar incident on March 2 killed Anthony Stephan House, 39, at his home, not far away.
In each instance, officials said the explosive packages were left at the doorsteps overnight and the residents opened them in the morning.
Manley also said the packages used were average size boxes that are "not exceptionally large" and were not from any of the official mail or delivery services.
"There are similarities, and we cannot rule out that these two incidents are in fact related," Austin Police Chief Brian Manley said at a news conference Monday.
The U.S. Postal Service said Monday's first package did not go through any of its facilities.
Manley warned residents to not open or take suspicious packages into their homes, encouraging them instead to call 911. Both attacks are being investigated by local and federal authorities.
Manley said police can't yet rule out hate crimes because residents of both targeted homes were African Americans and the third woman was Hispanic.
"We will not tolerate this in Austin," the police chief said.