Police in Austin are responding to another reported explosion - the sixth in a spate of bombings that have left two dead and four others seriously wounded.

Emergency services tweeted late on Tuesday that at least one person was injured after a reported blast at a shop in the south of the Texan city.

The explosion marked the latest in a string of blasts in the Austin area since 2 March.

However the Bureau of the Alcohol, Tobacco and Firearms and Explosives said it was an incendiary device rather than a package bomb and did not appear to be linked to the previous blasts, raising the prospect of a copycat attack.

The development came as the chairman of the US House Homeland Security committee said federal authorities had informed him that investigators have obtained surveillance videos in Austin that "could possibly" show a suspect in the earlier package bombing at a FedEx distribution centre near San Antonio.

Texas' Attorney General, Ken Paxton, said that package was sent from Austin and was addressed to a home in Austin. Four other package bombs have exploded in the city.

The latest explosion, at a Goodwill 'thrift' shop, left a man in his thirties with non-life threatening injuries.

Investigators have repeated prior warnings about not touching unexpected packages and urged people to be wary of any stray object left in public.

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Austin police say they have now responded to more than 1,200 reports of suspicious packages in a little more than a week — without finding anything dangerous.

Officers originally pointed to possible hate crimes, but the victims have now been black, Hispanic and white and from different parts of the city.