The latest blast occurred around 8:30 p.m. in a suburban neighborhood in southwest Austin.

Two men in their 20's were hurt and hospitalized with non-life-threatening injuries.

It was the fourth explosion to rock Austin in less than three weeks and police say the bombings are likely related.

Officials have been investigating the incidents as hate crimes since all the initial victims were black or Hispanic. But since the two latest victims were white, police now say they're not ruling out any possible motive for the bombings.

Police are warning residents not to touch any unexpected packages left at their homes. They say the latest explosion was detonated by a tripwire, "showing a different level of skill."

The first bombing took place on March 2, killing a 39-year-old man. Two more package bombs then exploded in front of homes on March 12, killing a 17-year-old, wounding his mother and injuring a 75-year-old woman.

Authorities are offering a $115,000 reward for information leading to the arrest of the bomber.

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