Update: Grand Fire in San Bernardino County is now 100% contained

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Updated: 10:39 a.m. May 18

First discovered: 5 days ago, 7:13 p.m. May 13

Initial location: Grand Avenue and Pleasant Hill Drive, Chino Hills, San Bernardino County, Calif.

Fire unit: Cal Fire San Bernardino Unit in Unified Command with Chino Valley Fire

Fire type: Wildfire

Fire name: Grand Fire

Grand Fire initially started 7:13 p.m. May 13 at Grand Avenue and Pleasant Hill Drive, Chino Hills in San Bernardino County, California.

Since its discovery five days ago, it has burned 36 acres. As of Monday morning, the blaze has been fully contained. Vahicle malfunction is believed to be the cause of the wildfire.

Fire containment

What does 100% containment mean?

Note that full containment doesn't mean the fire is completely out. In this case, it means that the wildfire has been fully enclosed by a control line and it is now stopped from spreading. A fully contained wildfire may continue to burn within the containment perimeter but is not likely to spread.

However, there's a significant difference between containing and controlling a wildfire. After the fire is fully contained, the next step is to control it. Controlling a fire means ensuring that the fire can't spread or cross the containment line.

Containment is part of a larger plan for managing a wildfire. It is normally expressed as a percentage and it refers to how much of the fire perimeter has been surrounded/enclosed by a control line that firefighters create. The containment percentage indicates a certain level of control, but it doesn't always correlate to safety level. Also, it's important to note that containment doesn't mean a fire is out.

How is containment measured?

The incident's central command constantly receives progress reports from firefighters on the ground. As the fireline is constructed, inspected or reinforced, mappers record those details to adjust the containment percentage. The percentage tells the public how much of the fire perimeter is believed to not go beyond the control lines.

Source: Cal Fire

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This story was originally published May 18, 2026 at 10:52 AM.