Two men were taken to the hospital with serious but non-life threatening injuries after an explosion in southwest Austin, Texas, on Sunday evening, authorities said.
Police were called to the scene at 8:32 p.m., in a city that has been rattled by a series of blasts.
The two injured men were in their 20s and taken to South Austin Medical Center, according to an Austin EMS tweet.
Police and the FBI responded to the scene Sunday. There was a second item, a backpack that police were clearing, said Austin Police Chief Brian Manley.
"It's obvious an explosion has occurred," he said at a late Sunday briefing.
The latest explosion comes less than a week after police said three package explosions that happened over 10 days were connected. Those explosions killed a man and a teenager, and injured two others.
The victims in those three explosions were African-American or Hispanic. Police have not yet discovered a motive, but have not ruled out the possibility the bombs could be hate crimes.
It's not clear if Sunday's explosion is related to the previous events.
Manley wasn't taking questions, but said another briefing would take place early Monday.
"Do not touch any packages or anything that looks like a package. Do not even go near it at this time," Manley told residents. "Given the darkness we have not had an opportunity to really look at this blast site to determine what has happened."
Resident: 'It's concerning'
Stan Malachowski, who lives about half a mile away, said he heard a loud explosion.
"It was loud enough to hear inside of our house with our windows and door shut. Again, airplanes go by and cars backfire so we didn't think much of it," he told CNN affiliate KXAN.
"This is a quiet neighborhood. It's a family neighborhood. It's concerning."
The Sunday incident was reported on Dawn Song Drive, with police warning residents in the immediate area to stay inside their homes until morning.
Many in Austin have been on edge since the bombings, as some residents of color in the Texas capital say they feel under threat.
The reward for information leading to the arrest of the person or persons responsible for the three explosions increased to a total of $115,000, authorities had announced earlier Sunday. Officials have urged residents to call in with tips to the police department, even if the information is seemingly "inconsequential."
South by Southwest wrapped up Sunday, but received a bomb threat Saturday, that resulted in the cancellation of a concert featuring The Roots.