Updated at 11:35 p.m. ET:
Authorities in Austin, Texas, responded to an explosion in the southwest part of the city late Sunday, with the city's emergency medical service tweeting that it caused two serious but non-life-threatening injuries.
The blast comes on the heels of three package-bomb explosions in recent weeks that have killed two people and wounded two more, as well as a bomb threat that canceled a Saturday hip-hop concert at the South by Southwest festival. It is not yet known if Sunday night's explosion is related to any of the prior incidents.