Police say 35-year-old Melissa Ketunuti was found in the basement of her home on the 1700 block of Naudain Street.
She had been hogtied and strangled with a belt around her neck and then set on fire.
Ketunuti's cause of death appeared to be strangulation, but police are awaiting the results of an autopsy.
When asked if there were any signs of sexual assault, Capt. James Clark of the Homicide Unit said during a news conference on Tuesday morning that while they were still awaiting those autopsy results, there were no immediate signs of sex assault.
Clark also said there were no suspects or a motive yet in this case.
Police questioned Ketunuti's boyfriend this morning and then brought him to the house this afternoon.
The police say, at this point, he is not a suspect.
Police are re-tracing the victim's steps from Monday morning, saying she can be seen on surveillance video and investigators have several receipts from that time.
They were looking for signs that someone might have been following her.
Clark said there was no sign of forced entry.
"We don't know if she walked in on individuals inside of her property; we don't know if individuals forced her inside of property," Clark said.
Clark also said it is not clear if the victim knew the killer or not.
Ketunuti, who lived alone, was a doctor taking part in a pediatric fellowship at Children's Hospital of Philadelphia.
"She dedicated her whole life to being a doctor and helping kids with cancer. It's very, very unfortunate that she died in this manner," said Clark.
Ketunuti was found in the basement of 1728 Naudain Street around 12:30 p.m. Monday by a pet walker who came to pick up her dog.
Firefighters and police were called to the scene.
"They go in the basement. They find a female - her body's on fire. The fire department puts water on her to put the fire out," Philadelphia Police Chief Inspector Scott Small said.
Neighbor Victor Pisani says Ketunuti lived at the home for a little over three years.
Another neighbor of the victim, Pamela Rimato-Tirone, is taking care of the her black Labrador Retriever. Rimato-Tirone said she walked by the home just 10 minutes before the body was found and nothing seemed suspicious.
"Everything was fine. I saw a guy going to visit [the home next door] because someone passed away, they were holding Shiva there today, everything was fine," Rimato-Tirone said.
There is a $33,500 reward offered for information leading to an arrest and conviction in the case. The Citizens Crime Commission is administering an $13,500 reward, and Philadelphia Police have posted a $20,000 reward.
Anyone with information is asked to call Philadelphia Police at 215-686-TIPS (8477), send a text message to PPD TIP (773847) or send a tip through phillypolice.com.
On Tuesday morning, Children's Hospital of Philadelphia said that Ketunuti was a second year infectious diseases fellow and researcher at CHOP.
"Melissa was a warm, caring, earnest, bright young woman with her whole future ahead of her," said Paul Offit, MD, chief of the Division of Infectious Diseases, in a written statement. "But more than that, she was admired, respected and loved by those with whom she worked here at CHOP. Her death will have a profound impact on those who worked with her and we will all miss her deeply."