Update: Simpson Fire in Riverside County hits 100% containment by Thursday evening

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Updated: 7:46 p.m. June 11

First discovered: 5 hours ago, 1:57 p.m. June 11

Initial location: Simpson Road and Briggs Road, Menifee, Riverside County, Calif.

Fire unit: Cal Fire Riverside Unit

Fire type: Wildfire

Fire name: Simpson Fire

Simpson Fire initially started today at 1:57 p.m. at Simpson Road and Briggs Road, Menifee in Riverside County, California.

After being active for five hours, it has burned 10 acres. By Thursday evening, a fire crew of 21 has achieved full containment of the fire. The cause is, however, still being investigated.

Six engines and one water tender have been combating the blaze. According to Cal Fire, "Numerous firefighting air tankers from throughout the State are flying fire suppression missions as conditions allow."

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 June 11, 2026 at 4:16 PM.