CHINO ( — Residents in an area of San Bernardino County Wednesday were ordered to shelter in place after a plume of gaseous smoke was reported.

Chino Valley Fire officials received a call at 7:39 a.m. and responded to the 11500 block of Yorba Avenue.

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A HazMat team discovered a small quantity of an unknown substance in a field behind a home.

“We know that it is off-gassing and it is buried in an open field,” Massiel Ladron De Guevara, of the Chino Valley Fire Dept., said. “Our HazMat team is in the process of going in and determining what that substance is.”

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The California Highway Patrol later said the plume was caused by buried pool chemicals that reacted with the rain.

A shelter in place order was issued for the area between Phillips Boulevard and Francis Avenue and Yorba and Norton avenues, but that order was lifted around 12 p.m.

Residents were told to keep all windows and doors closed for the duration of the incident.

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One person was transported to a local hospital in unknown condition.