Texas law enforcement is saying that a pair of package explosions at residences in Austin, Texas that left two people dead may be connected to an earlier incident.

On Monday, a package exploded in the face of a 17-year old boy killing him and injuring a woman at home, according to CNN. A 75-year old woman was left in critical condition after another reported explosion.

On March 2 an exploding package killed 39-year old Anthony Stephan House.

“The evidence makes us believe these incidents are related,” Austin, Texas, city Police Chief Brian Manley said on Monday at a news conference.

The victims were African-Americans and police officers are looking into whether the incidents are hate crimes, but have no official word on whether they were targeted for that reason, officials told CNN.

“We’re not ruling anything out at this point,” Manley said.

According to authorities, the packages exploded when the victims went outside and picked the packages up from their doorsteps; USPS, UPS or FedEx did not deliver them.

Texas Attorney General Ken Paxton warned all Austin residents to contact law enforcement if any suspicious packages arrive by mail.

“With three reported explosions in the Austin area, I want to urge all Texans to report any suspicious or unexpected packages arriving by mail to local law enforcement authorities,” Paxton tweeted.

Authorities are urging residents and visitors, who are there for the South by Southwest Interactive Festival to be careful.

“Enjoy yourself, have a good time,” Manley said. “But be aware, be suspicious.”