The Austin bomber has been shot dead as police FBI agents were trying to arrest him, it has been reported.

The man detonated a device before gunfire rang out along Interstate Highway 35 in the early hours of Wednesday, according to KVUE.

The FBI and police tracked the bomber to the Round Rock area using cell phone technology, security video, store receipts before 'engaging him' around 3am on Wednesday, the station reports.

As officers pursued the suspect a device was detonated, which had been anticipated by police, before a volley of gunfire.

The shooting comes just hours after CBS published CCTV showing the bombing suspect at a Fed-Ex office in the south of the city.

The images show a man, possibly wearing a wig and gloves, delivering two packages to the store around 7.30pm on Sunday.

One of the packages subsequently exploded on a conveyor belt at a FedEx sorting facility outside of San Antonio in Schertz. 

Timeline of Texas package bomb attacks

March 2: Anthony Stephan House, 39, is killed when a package blows up at 6.55am at his home on the 1100 block of Haverford Drive.

6.44am on March 12: Draylen Mason, 17, is killed and his mother is seriously injured in a package explosion in their kitchen on the 4800 block of Oldfort Hill Drive.

11.50am on March 12: Esperanza Herrera, 75, is severely injured in a package explosion while visiting her mother's home on the 6700 block of Galindo Street.

March 18: Two men in their 20s are seriously injured by a trip wire explosion on a sidewalk near the 4800 block of Dawn Song Drive.

Around 12.01am March 20: One man is injured in a FedEx facility in San Antonio when a package 'containing nails and pieces of metal' bound for Austin explodes. Wounded employee is taken to hospital with minor injuries.

6.19am March 20: Bomb squad responds to a FedEx sorting facility at 4117 McKinney Falls Parkway. An unexploded package bomb is secured. Police confirm it is connected.

The other was intercepted at a facility near Austin airport and was later confirmed to contain a bomb.

Authorities believe the same person is connected to the two packages that surfaced Tuesday is also responsible for the four other explosions that began on March 2nd, killing two people and injuring six.

Austin Police Department tweeted that they were working on an officer-involved shooting near the highway, but gave no further details.

The I-35 has been closed in both directions while images from the scene show dozens of law enforcement vehicles parked along the highway. 

The first incident occurred on March 2 when a package bomb exploded at a northeast Austin home, killing a 39-year-old Anthony Stephan House.

Two more package bombs then exploded further south on March 12. Draylen Mason, 17, was killed and his mother was wounded after they opened a package in their kitchen.

A 75-year-old Hispanic woman named by family as Esperanza Herrera was severely injured when a package bomb exploded at her home a few hours later.

The trip wire explosion on Sunday came just hours after police made an unusual direct appeal to whomever was responsible for three package bombs that killed two in the past month.