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As authorities in Boston investigated deadly explosions near the finish line at the Boston Marathon, public safety officials in the Bay Area reacted with caution and urged the public to have a heightened sense of awareness.

In San Francisco, uniformed officers will be on a "heightened patrol alert," and an increased police presence would be noticeable at tourist spots and other areas that attract large crowds, according to a spokesman for the San Francisco Police Department.

"Everything we're doing is simply precautionary at this stage," said Officer Albie Esparza. "There is no information or any credible source that suggests anything is not safe here. But we are telling people they should be alert."

A similar warning was communicated by BART officials, who said they also will have heightened patrols on trains, as well as increased security.

Passengers "are gonna see more officers out there," BART spokesman Jim Allison said. "The other thing that's important is that if somebody sees something (unusual), they need to say something."

In Oakland, police said that there would be a "more visible presence than normal" at major sporting events Monday evening, with both the Oakland A's and Golden State Warriors playing home games.

"Certainly there is heightened awareness," said Bob Rose, spokesman for the Oakland A's. "We will continue our normal game-day security procedures, which include hand-checking all bags brought into the Coliseum. Beyond that, we are working with our in-house security and the Oakland police and reminding our game-day and full-time employees to be extra observant."

According to Raymond Ridder, vice president of communications for the Golden State Warriors, there would be no major changes to security for Monday's game against the San Antonio Spurs.

"As of now, there is nothing heightened planned for tonight, though that could change upon further discussion with the Oakland Police Department," Ridder said. "Pretty much every night, we have heightened security and have Magneto-Meters at every door. Those will be in place as they are for every game."

San Jose police put out a news release saying the department had no plans to change how it deploys its officers.

Safety officials at the Golden Gate Bridge were monitoring the situation and were on alert status, but the day was proceeding normally otherwise, said Mary Currie, the public affairs director of the Golden Gate District.

In Southern California, law enforcement agencies in the Los Angeles area stepped up patrols Monday in the wake of the Boston Marathon explosions.

L.A. County Sheriff Lee Baca said his department was on "heightened alert" and had increased patrols at government buildings, shopping centers, athletic events and public transit centers.

Neither the county nor the city of Los Angeles had activated their emergency operations centers.

Boston police say at least three people were killed and dozens were hurt when a pair of bombs exploded near the marathon finish line.

Eric Hartley of the Daily News in Los Angeles and staff writers Natalie Neysa Alund and Erin Ivie contributed to this report.