SAN FRANCISCO (CBS SF) — San Francisco police are asking the public to help find a man with medical conditions who has been missing from his home in the Parkmerced area since Monday.

Lester Greene was last seen boarding a Muni .28-line coach in the Taraval District since about 5 p.m., reportedly heading to the University of California, San Francisco Medical Center on Parnassus Avenue.

Police said Greene, who is considered at risk due to medical conditions, frequents Hayes Valley and downtown.

Greene is 70 years old, Black and last seen wearing a black beanie, black pea-coat, black sweatpants, and athletic shoes.

Anyone who sees him should call police immediately and be prepared to provide his current location and clothing description.

Anyone with information regarding this investigation is asked to call the 24-hour tip line, (415) 575-4444.

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