A southern Illinois sheriff says four people were injured after an oil-field explosion perhaps sparked by a welding job.

White County Sheriff Doug Maier says injuries to three victims burned during the blast Tuesday near Norris City were "very serious." They were hospitalized. A spokeswoman for El Dorado's Ferrell Hospital, Heather Morris, says 1 of those victims was transferred to another hospital with burns over half of his body.

The fourth victim was treated at the El Dorado hospital and released.

The sheriff says a preliminary investigation shows welders were working on a tank when something ignited. Norris City firefighters quickly doused the blaze.

State fire investigators are assisting in the probe.

Norris City is a 1,000-resident village near the Illinois-Indiana state line, about 50 miles west of Evansville, Ind.