Published: May 05, 2010 7:02 PM EDT

SAN ANTONIO  - An 18-wheeler truck being loaded with fuel at a San Antonio refinery has exploded, setting off a chain reaction of smaller blasts and leaving some workers hurt.

A giant plume of black smoke could be seen over San Antonio's southeast side after Wednesday morning's blast at the AGE Refining Inc. facility.

Fire department spokeswoman Deborah Foster says authorities are trying to account for all 100 employees and that some workers are being treated at the scene.

No numbers were immediately provided. Foster says authorities are evacuating residents from their homes within a one-mile radius.