AUSTIN, Texas — Package bombs that killed a teenager and wounded two women Monday in Austin are probably linked to a similar bombing that killed a man in the city earlier this month, authorities said.
The first of Monday’s attacks killed a 17-year-old man and wounded a 40-year-old woman, both of them black.
As Police Chief Brian Manley held a news conference to discuss that blast, officers were called to the scene of another explosion. A 75-year-old Hispanic woman was taken to a hospital with potentially life-threatening injuries.
Authorities suspect that both of Monday’s blasts are linked to a March 2 attack that killed a 39-year-old black man, and they urged the public to call police if they receive any unexpected packages.
Manley at first suggested that the blasts could constitute a hate crime, but he later amended that to say authorities had not settled on a motive.
‘‘We are not ruling anything out at this point,’’ said Manley, who said the intended targets were not clear since multiple people live in the homes where explosives were placed. ‘‘We are willing to investigate any avenue that may be involved.’’
The police chief refused to provide many details about the explosives, citing the ongoing investigation. But he said they were an ‘‘average size letter box’’ and ‘‘not particularly large.’’
In all three cases, he said, the packages did not appear to have gone through the Postal Service or private carriers such as UPS but were left on doorsteps without a knock or ringing of doorbells.
The explosions happened during the South by Southwest music, film and technology festival, which brings about 400,000 visitors to Austin each year.
The police chief urged visitors to ‘‘be aware of what’s going on.’’
‘‘Enjoy yourself. Have a good time,’’ he said. ‘‘There’s no reason to believe that you are at any greater risk other than be aware, look for things that are suspicious.’’
Four years ago, a driver plowed through a barricade and into festival-goers, killing four people and injuring many others. Additional security measures were taken in the aftermath, including additional policing, tougher security checks, and brighter street lighting.
The three explosions occurred in different parts of East Austin.
Monday’s first explosion happened at a home in Springdale Hills, a leafy neighborhood of houses mostly from the 1960s and 1970s. After the attack, officials in hazardous materials suits came and went regularly.
The blast was about 12 miles from the home where the March 2 package bomb killed 39-year-old Anthony Stephan House. His death was initially investigated as suspicious but is now viewed as a homicide.
The second explosion Monday happened in the Montopolis neighborhood, near the airport and about 5 miles south of the day’s first blast.
Joanna Samarripa, who lives around the corner, said she saw a woman slumped in the doorway of the home after the blast.
‘‘The cops were running and telling everyone ‘Get out of the house! Get out of the house!'’’ Samarripa said. ‘‘I’m still scared. I’m still shaking. I don’t even want to leave my daughter no more.’’
Neighbor Keith Reynolds heard what sounded to him like a propane explosion. He rushed outside and saw a cloud of hazy smoke and others on his street running to help.
‘‘There was a horrible screaming. You knew that something terrible was happening,’’ Reynolds said, adding that the victim’s body was riddled with holes as emergency responders took her out of the house and into an ambulance.
‘‘It’s just a regular family neighborhood,’’ he said. ‘‘It’s just a grandmother, you know what I mean? Like, why?’’
FBI teams from Austin, San Antonio, and Dallas were investigating as was the Bureau of Alcohol, Tobacco, Firearms and Explosives. Manley said anyone receiving a package they were not expecting should call 911.
‘‘Under no circumstances should you touch them, move them, or handle them in any way,’’ he said.
LaVonne Mason, cofounder of the Austin Area Urban League, said her grandson was the 17-year-old victim killed, but she declined to say anything further. Her husband, Norman Mason, is a well-known dentist in the East Austin area and a longtime mentor to black student athletes at the University of Texas.
Relatives on the scene identified the woman injured in the third blast as Esperanza Herrera, according to The Washington Post.