The reported explosion on Tuesday evening that injured one man in Austin, Texas, was an incendiary device, not a package bomb, police say.
They say that at this time they have no reason to believe "this incident" is related to recent package bombs in the area that killed two people.
President Donald Trump said "sick people" carried out those blasts.
The authorities said the earlier blasts - involving package bombs and a tripwire - were related.
Another package bomb "was disrupted by law enforcement", police said.
On Tuesday evening, the Austin fire department said a man in his thirties received "potentially serious" injuries in the explosion at the Goodwill charity shop on Brodie Lane.
FINAL Multiple assets #ATCEMS @AustinFireInfo @Austin_Police on scene Brodie Ln/W Slaughter Ln (1902) reported explosion: #ATCEMSMedics transported ~30s male with potentially serious, not expected to be life threatening, injuries to St Davids South Austin. No further info avail.— ATCEMS (@ATCEMS) March 21, 2018