Texas explosions: New Austin blast 'may be tripwire-activated'Police in Austin, Texas, have warned the public that a fourth explosion there may pose a new threat. Police have sealed the area around the scene of the blast -- Photo: REUTERSThey said they were investigating reports the explosion, which injured two people, was activated by tripwire. The police they say they are working under the belief that the explosions are connected. The latest blast came hours after officials announced a new $100,000 (£71,000) reward for information. He added: "We do believe that this was a bomb that exploded, but it was not similar to previous explosions.