A two-alarm fire tore through a unit of a six-unit apartment complex on Highland Avenue in San Mateo early Friday morning, sending two residents to the hospital and killing their dog. Firefighters contained and extinguished the flames in less than 30 minutes, but the damage left the unit unlivable and its occupants displaced.
The fire broke out at 839 Highland Ave, just south of the Burlingame border, according to the San Mateo Daily Journal. The San Mateo Consolidated Fire Department responded at about 2:20 a.m. Friday, according to the Daily Journal.
The two people hospitalized were residents of the unit where the fire started, and their dog also lived in that same unit, the Daily Journal reported. No injuries were reported outside the affected apartment, and the rest of the six-unit building was not affected by the blaze, per the same account.
Mass Casualty Protocol Triggered During Response
The fire triggered a Level 1 Mass Casualty Incident activation, the station's report notes. The Coastal Valleys EMS Agency's plan outlines the purpose and authority for mass-casualty response.
It is not the first time this protocol has come into play for San Mateo County's Peninsula fire crews. In December 2025, San Mateo Consolidated Fire Department crews responded to a two-alarm apartment fire on Edgewater Boulevard in Foster City that also triggered a Level 1 MCI activation after at least five residents were rescued, as reported by OnScene TV.
Older Building in a Dense Rental Corridor
North Central San Mateo is a densely populated, historic neighborhood near the Burlingame border that features one of the highest concentrations of multi-family rental housing and small apartment units in the city, according to NeighborhoodScout. The two-story, six-unit building was constructed in 1970 and sold in August 2024 for $3.35 million after remaining under single-family ownership for more than 50 years, per Redfin property records.
The fire-damaged unit is now unlivable due to extreme heat, smoke and water damage, leaving its residents displaced while the cause of the fire remains under investigation, the Daily Journal reported. Fire officials have not said what sparked the blaze or how it started inside the unit.
A Consolidated Department Built for Rapid Response
The San Mateo Consolidated Fire Department, which responded to the Highland Avenue call, officially began operations on January 13, 2019, after the cities of San Mateo, Foster City and Belmont formed a Joint Powers Authority to consolidate their individual municipal fire agencies, according to the San Mateo Consolidated Fire Department. The agency now operates 10 engine companies and two 100-foot tractor-drawn aerial ladder trucks across nine stations, serving roughly 161,000 to 164,000 residents across the three cities.
Under its adopted Standards of Cover performance metrics, the department aims to arrive at 90 percent of all Priority 1 emergency calls within six minutes and 59 seconds, a benchmark that underscores how quickly crews are expected to reach calls like Friday's fire. The department also contracts with San Mateo County to operate the countywide Hazardous Materials Emergency Response Team, a Cal OES-certified Type 1 unit serving all 20 cities in the county, though that specialized unit was not reported as part of Friday's response.
Friday's fire echoes a similar incident Hoodline covered in January 2025, when San Mateo Consolidated Fire Department crews contained a unit fire on North Amphlett Boulevard that left one resident hospitalized and a dozen others displaced. No cause has yet been announced for the Highland Avenue fire, and the condition of the two hospitalized residents has not been publicly disclosed.
