Authorities said five train cars overturned outside of San Antonio, spilling about 1,000 gallons of sodium hydroxide and prompting a temporary evacuation.
Bexar County Sheriff's Office spokeswoman Monica Ramos told the San Antonio Express News the derailment happened around 4 p.m. Sunday in an industrial area southwest of the city.
Ramos said the sodium hydroxide didn't cause fumes or residue, adding that sodium hydroxide is only dangerous if touched.
She said two men inside a tug car that overturned suffered minor injuries and were treated on scene before being released.
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A nearby flea market was temporarily evacuated.
KENS-TV reported the rail line involved is privately owned by oilfield services company Schlumberger.
An environment group is cleaning up, and authorities are investigating the cause of the derailment.