FRESNO (CBS13) – A major explosion and fire is being reported in Fresno Friday afternoon.

Authorities say the explosion happened in a construction area near the Fresno County Sheriff’s gun range. According to preliminary information from California Highway Patrol, multiple people have been burned.

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Southbound Highway 99 has reopened, but northbound Highway 99 remains closed. Traffic is being diverted onto Highway 41.

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PG&E says it is investigating the situation.

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Three people who were injured in the explosion are in critical condition at Community Regional Medical Center in Fresno, according to hospital spokesperson Mary Lisa Russell.