PHILADELPHIA (CBS) — Homicide detectives say human remains have been found a short distance away from where missing 20-year-old Jimmy Mao was last seen. The remains were found inside a black duffel bag on the 1000 block of Cobbs Creek Parkway.

Police sources say the remains “have been there for a while.”

Investigators say there is one body on the scene.

Philadelphia Police Chief Inspector Scott Small says the victim had neck and head wounds.

“It appears to be an Asian male,” Small said. “Police believe, based on tattoos and other information, that they know who the body is, but at this time it has not been positively identified.”

Mao’s sister says she is holding out hope that he is still alive.

“My head is everywhere right now. I can’t talk,” Niki Mao said.

Niki and other family members spoke with homicide detectives Wednesday evening. She says the family is being asked to meet at the Medical Examiner’s Office Thursday morning to identify the body.

“Hopefully it’s not him. I’m just going to wait until tomorrow,” Niki said.

Philadelphia SVU put out a plea for the public’s help to locate Mao on Friday and again this morning. The family previously received a text demanding ransom.

Police say the last person to see Mao was the 17-year-old person of interest in the fatal stabbing of his foster mother, 64-year-old Renee Gilyard, whom sources tell CBS3 knew Mao through foster care placements.

“We did interview him and he could not shed further information about his whereabouts,” Philadelphia Police Capt. Mark Burgmann said.

The 17-year-old was picked up this morning after police identified him as a person of interest in the murder of his foster mother in East Germantown. Gilyard’s body was found in the bathtub inside her home.

“Two knife wounds to the left side of her neck,” Philadelphia Police Capt. Jason Smith said.

Police would not reveal how they made the connection between the two cases.

Police also indicated they were searching for a second missing person identified as 16-year-old Jacob Merritt-Richburg. Investigators say Jacob was last seen Jan. 6. His family reported him missing this past Saturday.

“During our investigation, we also came across someone named Jacob Merritt Richburg, a 16-year-old from 1800 Vineyard Street,” Burgmann said. “We believe he is some type of acquaintance of Jimmy Mao and we believe he may be in possession of property that belonged to Jimmy Mao.”

Niki Mao says the 17-year-old person of interest and her brother lived at the same foster home on Angora Terrace.

CBS3’s Joe Holden and Greg Argos contributed to this report.