Police are responding to another explosion in Austin, Texas, which left a woman badly injured, hours after a package bomb killed a teenager and wounded a woman in a different part of the city.
Austin-Travis County emergency services tweeted that an explosion today in south-east Austin injured a woman in her 70s, who has been taken to hospital.
A second woman from that address has also been taken to hospital with an unrelated medical issue.
Authorities have not said whether the most recent explosion was caused by a package bomb like the one which exploded earlier today.
Police chief Brian Manley said at a news conference that investigators believe the deadly blast is linked to a package bomb on March 2 which killed a 39-year-old man in another part of the city.
"These [packages] are not coming through the United States Postal Service that we've determined at this point," official says on two deadly package explosions in Austin, Texas. https://t.co/fd4bcvtMyn pic.twitter.com/2OKsTpDVQf— CBS News (@CBSNews) March 12, 2018
It follows reports that another exploded package inside another house in Austin which killed a teenager and wounded a woman, is believed to be linked to a third deadly package sent to another home in Texas' capital city earlier this month.
Austin police chief Brian Manley said investigators believe the attacks are linked because in each case, the package bombs were left on the victims' front doorsteps, and not delivered by a mail service.
He said the US Postal Service does not have a record of delivering a package to the Austin home where the explosion occurred. He said that package was brought into the kitchen where it detonated, killing a 17-year-old boy and injuring the woman.
Mr Manley said investigators believe the explosion is linked to a similar blast that killed a 39-year-old man on March 2. That explosion occurred about 12 miles north of Monday's blast. Both explosions occurred in the early hours.
The chief said all of the victims have been black and that investigators are considering whether race could have factored into the attacks.
The FBI is helping Austin police in the investigation.