Seventeen fire departments from across the region participated in the exercise, using a controlled burn near Hesperia to practice fire-suppression techniques.

The tornado-like phenomenon occurs when intense heat causes air to rise and spin, with ash, embers and debris mixing into a rotating column.

To mark Arson Awareness Week, the San Bernardino Co. Fire Department is highlighting two hard-nosed fire investigators, along with their human partners.

Cal Fire crews have stopped the forward progress of an almost 10-acre vegetation fire that threatened structures in San Bernardino County Thursday afternoon. The Acorn Fire was burning off State Route 138 at Acorn Drive in Piñon Hills.