UPDATE: San Francisco police say they found an 11-year-old boy who went missing Monday and was considered at risk due to preexisting medical conditions.
The boy was seen at his home at 7:50 a.m., police said, and then went missing in the days to follow.
The child frequently rides Muni in Downtown, sometimes takes BART and is known to frequent the Metreon mall.
Police described him as 5-foot-4 and weighing around 105 pounds with black hair and brown eyes.
Humphrey was last seen wearing a black hooded sweatshirt with a purple Adidas logo, a light blue T-shirt, blue sweatpants and blue Vans shoes.
Anyone who locates Humphrey should call 911 and report his current location and physical description.
Anyone with information on his possible whereabouts should call the SFPD tip line at 415-575-4444 or text a tip to TIP411 and begin the text message with SFPD. You may remain anonymous.