Three package explosions in Austin, Texas, this month are believed to be linked, police say.

The Austin police chief said that three of the victims were black and one was Hispanic, and that investigators were considering whether race could have factored into the attacks.

The explosion Monday happened amid hundreds of thousands of people visiting the city for the South by Southwest festival.

AUSTIN, Texas — Package bombs that killed a teenager and wounded two women Monday in Austin are most likely linked to a similar bombing that killed a man in the city earlier this month, authorities said, and investigators are considering whether race was a factor because all of the victims were nonwhite.

The first of Monday's attacks killed a 17-year-old boy and wounded a 40-year-old woman, both of them black. She remains hospitalized.

As Austin's police chief, Brian Manley, held a news conference to discuss that blast, officers were called to the scene of another explosion that injured a 75-year-old Hispanic woman. She was taken to a hospital with potentially life-threatening injuries.

Authorities suspect that Monday's blasts are linked to a March 2 attack that killed a 39-year-old black man. They urged people in the area to call the police if they receive any unexpected packages.

The city is currently hosting the weeklong South by Southwest music, film, and technology festival known as SXSW, which brings about 400,000 visitors to Austin each year. The explosions happened far from the festival's main events, and there was no immediate word from organizers about additional safety precautions.

Four years ago, a driver plowed through a barricade into festivalgoers, killing four people and injuring many others. In the years since, it has added security measures such as increased policing, tougher security checks, and brighter street lighting, among others.

3 package bombs appear to be linked

The three explosions this month occurred in different parts of Austin.

The first explosion on Monday happened at a home near the city's Windsor Park neighborhood, about 12 miles from the home where the March 2 package bomb killed Anthony Stephan House.

His death was initially investigated as suspicious but is now viewed as a homicide. That bomb was big enough to destroy the front porch of the house, Manley said.

The second explosion on Monday happened in the Montopolis neighborhood, near the airport and about 5 miles south of the day's first blast.

In at least the first two blasts, the packages were left overnight on the victims' doorsteps and were not mailed or sent by a delivery service.

Manley said neither the US Postal Service nor private carriers such as UPS or FedEx had any record of delivering a package to the home where Monday's explosion occurred.

Attacks could be racially motivated

Authorities investigate the scene in East Austin on Monday. Ricardo B. Brazziell/Austin American-Statesman via AP Investigators haven't determined a motive for the attacks, but Manley said it was possible the victims could have been targeted because they are nonwhite.

"We don't know what the motive behind these may be," he said earlier Monday. "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 also said authorities were looking into whether the victims knew one another or ever crossed paths.

Special Agent Michelle Lee, a San Antonio-based spokesman for the FBI, said the agency "responded to both events" and was assisting Austin police taking the lead on investigating. She said the Bureau of Alcohol, Tobacco, Firearms, and Explosives was taking the lead on the federal investigation.

Manley said the US Postal Service was also involved.

"It's not time to panic, but it's time to be vigilant, and it's time to pay attention," Manley said on Monday afternoon. "It's time to pull together as a city and a community and solve this."