HOUSTON, March 20 (Xinhua) -- A worker was injured in an explosion early Tuesday morning at a FedEx Corp. distribution center near San Antonio, about 310 km west of Houston in the U.S. state of Texas, officials said.

A medium-sized package exploded at around 1 a.m. local time (0500 GMT) at the distribution facility in Schertz outside San Antonio, the San Antonio Fire Department said on Twitter.

The Schertz Police Department said investigations revealed a package in the sorting area as the source of the blast. One worker was treated for injuries.

The Bureau of Alcohol, Tobacco, Firearms and Explosives and the Federal Bureau of Investigation agents were also on the scene to investigate. This is the fifth parcel bomb explosion in Austin this month. Two people have died and over five sustained injuries so far.