Three Bay Area counties recorded the highest number of new coronavirus infections since the start of the pandemic on Saturday as California undergoes a surge and public health officials put in new restrictions to slow the spread.

Santa Clara, San Mateo and San Francisco counties recorded the most new cases since this news organization began tracking coronavirus infection data in April, an alarming development that officials say could warrant another lockdown. Altogether, the Bay Area recorded 2,281 new cases of the virus and six new deaths, for a total of 149,004 cases and 1,962 deaths.

The new cases come a day after San Mateo and San Francisco counties were moved from the “red” restriction level to the much more stringent “purple” level, joining the rest of the Bay Area in the most restrictive level. The two counties joined Lake, Calaveras, Plumas and Modoc counties too.

Santa Clara County recorded 747 new cases on Saturday for a total of 33,732, the most it has recorded since the start of the pandemic, and counted no new deaths to add to the total of 476. County officials on Saturday released new restriction in light of the rising caseload and instituted a ban on all on all professional, collegiate and high school sports.

Officials also issued a mandatory quarantine for those traveling into the region from more than 150 miles away and new capacity limits for indoor businesses.

The restrictions came just hours after a rollback from San Francisco and San Mateo counties, which both recorded record numbers Saturday. San Francisco, which had been championed as the state’s model for coronavirus prevention, recorded 256 new cases for a total of 15,342. In the city, 160 people have died from the virus and officials recorded no new deaths.

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In San Mateo County, officials on Saturday reported 441 new cases — the most ever — for a total of 14,148. One-hundred-and-seventy people have died in the county from coronaries, and officials did not report new deaths.

In the rest of the Bay Area, caseload numbers are also rising, though not as dramatically.

In the East Bay, Alameda County recorded 259 new cases and six new deaths for a total of 29,116 cases and 511 deaths. Contra Costa County recorded 324 new cases and no new deaths for a total of 23,895 cases and 261 deaths.

The North Bay counties of Sonoma, Napa, Solano and Marin together reported 254 new cases and no new deaths for a total of 32,771 cases and 384 deaths.