Photo: Contributed

UPDATE 7:35 a.m.

A package bomb that authorities believe is linked to the recent string of Austin bombings exploded early Tuesday inside of a FedEx distribution centre near San Antonio, leaving one worker with minor injuries.

Hours later, police sent a hazardous materials team to a FedEx facility in Austin to check on a suspicious package there. There was no immediate word about whether that package contained a bomb.

FBI agent Michelle Lee said the explosion happened at around 1 a.m. at a FedEx facility in Schertz, which is just northeast of San Antonio and about 60 miles (95 kilometres) southwest of Austin. One worker was treated for minor injuries and released, according to statements issued by the Schertz Police Department and FedEx.

Lee said that although it is still early in the investigation, "it would be silly for us not to admit that we suspect it's related" to the four Austin bombings that have killed two people and injured four others since March 2. She didn't have details about the size, weight or description of the package.

ORIGINAL 5:05 a.m.

A package bomb exploded shortly after midnight Tuesday inside a FedEx distribution centre in Schertz, Texas, and the FBI and ATF are at the scene, spokeswomen for both agencies told The Washington Post.

The explosion happened occurred at a facility in Schertz, Tex., just northeast of San Antonio sometime around 1 a.m., said FBI Special Agent Michelle Lee. ATF spokeswoman Nicole Strong said that early indications are that no one was injured.

The Associated Press reported erroneously earlier Tuesday that the San Antonio Fire Department said one person had suffered a non-life-threatening "percussion-type" injury from the blast. That information came from SanantonioFIRE, a local media website that reports on local police, fire and emergency service news, and could not immediately be independently confirmed.

The blast follows a Sunday night blast that was triggered along a street by a nearly invisible tripwire, suggesting a "higher level of sophistication" than agents saw in three early package bombs left on doorsteps. It means the carnage by a suspected serial bomber that has terrorized Austin for weeks is now random, rather than targeted at someone in particular.

William Grote says Sunday's attack the latest left what appeared to be nails embedded in his grandson's knees.

Two people are dead and four injured, and authorities don't appear closer to making any arrests in the five bombings.

Authorities haven't identified Sunday night's victims, but Grote told The Associated Press that his grandson was one of the two men wounded in southwest Austin's quiet Travis Country neighbourhood. They suffered what police said were significant injuries and remained hospitalized in stable condition.