Police say they have found concrete evidence a 23-year-old was behind a bombing spree in the US state of Texas, by revealing that the bomber's mobile phone had a 25-minute recorded confession detailing each of the six explosives he made, leaving them confident none are still waiting to detonate.

The suspect, Mark Anthony Conditt, steered his car into a ditch and blew himself up on Wednesday.

No motive has been identified at this point, according to Austin police.

Al Jazeera's John Hendren reports from the Conditt's hometown of Pflugerville.