Swimmer vanishes after possible shark encounter off California coast during group outing

A woman who went missing while swimming on Sunday may have encountered a shark off the California coast, authorities said. 

The unidentified 55-year-old swimmer was reported missing off Lovers Point in Pacific Grove at around noon, the U.S. Coast Guard said in a joint statement Sunday with the cities of Pacific Grove and Monterey.

Two witnesses told authorities that the woman may have come into contact with a shark. The Pacific Grove Police Department told CBS News that the incident was being treated as a possible shark attack. 

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"We had a swim club that does a weekly swim out here off Lovers Point," Brian Anderson, a commander with the Pacific Grove Police Department, told CBS San Francisco. "They immediately called all the swimmers in and there was one swimmer who hasn't reported back yet." 

Coast Guard Petty Officer Christopher Sappey recalled one person's shark sighting to SF Gate. 

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"The person who reported the shark sighting claimed they saw a shark breach the water with what appeared to be a human body in its mouth," he said. "They then witnessed the shark submerge below the waterline without resurfacing."

The Coast Guard told Fox News Digital that it couldn't confirm that the case is "correlated with the report of a witnessed shark attack due to insufficient evidence."

A search effort was launched but by 8 p.m. Sunday, the woman was still missing, the Coast Guard said. Efforts were expected to resume Monday morning. 

Lovers Point Beach, as well as McAbee and San Carlos beaches, will remain closed through Tuesday. 

A beach advisory will remain in place for Asilomar State Beach, Monterey Municipal Beach, Del Monte Beach and Monterey State Beach through Tuesday, SF Gate reported. 

Fox News Digital has reached out to the Pacific Grove Police Department,