Ketunuti's boyfriend, Surya Mundluru, a doctor who lives in New York, has been ruled out as a suspect, police said. Authorities also have eliminated as a suspect the dog walker who cared for her beloved black Lab mix, Pooch - the person who found her still-burning body in the basement of her rowhouse on a quiet block of Naudain Street near 17th.
Police said Tuesday that whoever killed Ketunuti, 35, a Stanford University graduate who moved to Philadelphia in 2008 for a pediatrics fellowship at Children's Hospital of Philadelphia, strangled the petite, fit woman with a rope before setting her body ablaze.
Her body was found with the rope still around her neck, police said.
Ketunuti had spent the morning shopping, and detectives spent Tuesday retracing her steps and visiting area residents and merchants in search of surveillance tape that could help crack the mystery, Clark said. A $20,000 reward is being offered for information leading to the conviction of her killer.
Police found no sign of forced entry at her house, but Clark declined to say whether detectives found any evidence of a struggle. Detectives do not believe she was sexually assaulted, he added.
Investigators said Ketunuti had no known disputes with anyone, Clark said. He said he was unsure if anything had been stolen from her home, but investigators said initial reports that the woman's purse had been taken were inaccurate.
Ketunuti's brutal murder so far has vexed investigators, rocked her neighborhood and left her colleagues at CHOP in shock.
"It's going to be just a horrible thing for her family. It's a great disappointment," said neighbor Pamela Rimato Tirone, who was caring temporarily for Pooch on Monday night. "It's such a horrible thing."
CHOP on Tuesday released a statement that the community there is "deeply saddened" by the loss of Ketunuti, a second-year infectious-diseases fellow and researcher who worked at the hospital five years.
"Melissa was a warm, caring, earnest, bright young woman with her whole future ahead of her," said Paul Offit, chief of the Division of Infectious Diseases. "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."
Ketunuti moved to Philadelphia from Washington, D.C., where she had interned in surgery at Georgetown University Hospital and worked at a Veterans Affairs hospital. She came here for a pediatric residency, according to a blog she once kept. Her mother is Belgian, and her father, Thai; the family considered Bangkok home, according to the blog.
Ketunuti's blog leaves behind a haunting reminder of the promise lost when the killer violently ended the woman's life. She posted photos from her graduation and from trips to both of her parents' home countries, excitedly detailing her travels and experiences.
"My mother's old elementary school," the woman wrote in a 2007 post about Belgium. "She was, at the time, the only girl attending an all-boys school. Here, she perfected her shin kicks and punches!"
In a June 16, 2007, entry, she shared photos from her graduation day, when the young, pretty woman beamed bright-eyed at the camera, her dark hair barely grazing her shoulders from under a gold-tasseled cap.
"Finally the MD diploma!" she wrote that day. "Half is for me, and the other half belongs to all those who supported me along the way! Thank you!!!"
In Philadelphia, Ketunuti was known by neighbors as a pleasant woman devoted to her work, fitness and Pooch. She also was an avid runner who completed many distance runs.
She researched AIDS in Botswana in 2005 for the National Institutes of Health.
Late Tuesday, investigators in the homicide unit who worked the case all day said they had "nothing solid" on the case. They said they had conducted several interviews but had not determined a suspect, motive or any leads in the case.
Clark appealed to the public for tips to help solve Ketunuti's murder, one of six homicides over the holiday weekend. Anyone with information about the case should call detectives at 215-686-3334 or -3335.
On Twitter: @DanaDiFilippo