Redwood City police say a citizen who saw an alert on Twitter helped locate a missing elderly woman on Thanksgiving Day, highlighting the power of social media.

The 77-year-old woman, who had only recently arrived in the United States from Japan and spoke no English, was reported missing by her family shortly before 2:30 p.m. on Thanksgiving Day, Sgt. Rhonda Leipelt said.

The family, who lived on Sussex Way, suspected that the missing woman had taken her customary morning walk and lost her way in the unfamiliar streets. They feared she might have been walking since early in the morning.

Police began a labor-intensive process of calling hospitals, canvassing neighborhoods, sending alerts to other agencies and the press and bringing out additional patrol and K-9 resources for a structured search, Leipelt said.

And then, around 6:10 p.m., a message went out to the more than 1300 residents who have subscribed to email and text alerts and to the police department's Facebook and Twitter accounts.

Less than 15 minutes later, a resident three miles from the family's home called police to say he had seen the missing woman on his street. He recognized her and called police after seeing the alert on Twitter.

The woman was located a short time later and returned to her family.

"Our community is moving beyond fixed geographic boundaries and we are only limited by our citizen's willingness to engage with us in the virtual Redwood City community," Leipelt said. "The Redwood City Police Department is actively engaged and this event clearly demonstrates how an effective public-police partnership can enhance the level of service we are able to provide."

Residents can sign up for alerts at www.nixle.com or by texting their zip code to 888777.