Despite its closed parking lot and warnings from police, Linda Mar Beach in Pacifica was anything but deserted Sunday evening.

About 30 or 40 surfers floated on their boards, back-lit by the sun, waiting for a decent set to roll in. Dozens of people walked along the beach, a few stopping to sit in the sand. Social distancing was hit or miss.

Over the three-day weekend, April 17-19, 275 people were ordered off the beach for violating the Bay Area’s toughest shelter-in-place order during the coronavirus pandemic, according to Pacifica police.

In a statement released Monday, Pacifica Police Chief Daniel Steidle said officers approached 408 beach-goers and asked where their residence is located. A total of 275 were ordered to leave after admitting they were more than five miles away from home.

San Mateo County is the only Bay Area county that mandates citizens must stay within five miles of their homes for all nonessential trips or activities during the pandemic.

Pacifica police also counted vehicles parked on streets near the beach and found that almost half (45 percent) were more than five miles from where they were registered, Steidle said.

Mayor Deirdre Marting threatened close the beaches altogether if people continue to flout the order.

“The data we’ve collected and the enforcement we’ve had to take suggests many are not taking these orders seriously,” Martin said in a statement. “This is alarming because unsafe conditions are occurring and, as a result, the City, in coordination with the State, may be left with no choice but to close the beaches entirely to everyone unless conditions improve.”

ALSO: Santa Cruz beaches reopen, but drone shows deserted waterfront, Boardwalk

Pacifica wasn’t the only area slammed by an influx of visitors. The county Sheriff’s Department issued 650 warnings over the weekend and four formal citations along the coast.

“We had hundreds of people on the beach and practically anywhere they could find a place to sit along the coast line,” Lt. Stephanie Josephson said in a written statement. “Most families encountered had packed their family vehicle with bags of toys, food and items for a full day at the beach. Most people seemed to be aware of the health orders but decided to take the chance in coming out to the beaches and complied with the verbal warnings.”

Exceeding the five-mile radius from your home in order to go to the beach is not the only way to attract police attention in San Mateo County. Bicyclists riding on Route 1 and other highways have been stopped and issued warnings.

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Mike Moffitt is an SFGATE Digital Reporter. Email: moffitt@sfgate.com. Twitter: @Mike_at_SFGate