Investigators believe that a series of deadly package explosions in Austin could be racially motivated. 

Austin police are investigating a third explosion Monday, nearly six hours after a similar blast killed a teenager and 10 days after a man was killed by a device left on his front porch, according to the San Antonio Express-News.

Austin Police Chief Brian Manley said the first two packages were sent to the homes of African-Americans.


"We don't know what the motive behind these may be," Manley said. "We do know that both of the homes that were the recipients of these packages belong to African-Americans, so we cannot rule out that hate crime is at the core of this. But we're not saying that that's the cause as well."

Manley said they believe the attacks are related because packages were left on the victims’ doorsteps overnight, the Express-News reported. 

The U.S. Postal Service, FedEx and UPS do not have any records of delivering the packages. 

The first explosion killed 39-year-old Anthony Stephan House on March 2, CBS News reported. 

The second explosion, occurring before 7 a.m. on Monday, killed a 17-year-old boy and wounded an adult woman. 

The third explosion happened around noon on Monday, sending a woman in her 70s to the hospital with “serious potentially life threatening injuries,” the Express-News reported. 

Police are warning the public to not open any packages they aren’t expecting or any that look suspicious. 

The FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives are assisting with the investigation.