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Crews from multiple fire agencies responded to a brush fire that shut down lanes on the westbound 118 Freeway in the Chatsworth area Tuesday.

The so-called Peak Fire burned about 20 acres near Topanga Canyon Road after erupting around 11:30 a.m., said the Ventura County Fire Department, which assisted the L.A. county and city fire departments in the incident.

Two firefighters— one with VCFD and the other with the Los Angeles Fire Department—received treatment for heat-related health issues they suffered while battling flames on steep terrain amid 90-degree temperatures, officials said. Their conditions have since stabilized, according to VCFD.

The flames broke out in the area of the Santa Susana Pass, where forecasters said westerly winds were blowing and the relative humidity was 35%.

The blaze prompted the California Highway Patrol to block the Nos. 2, 3 and 4 lanes of the westbound 118, as well as the Topanga Canyon on-ramp. They could remain closed through 3 p.m., the Highway Patrol said.

“Expect heavy delays and avoid area as possible,” CHP’s West Valley station tweeted.

The fire was 40% contained as of 1 p.m., according to the L.A. County Fire Department.