ROME (AP) - A University of Washington student under investigation in the slaying of her British roommate in Italy must remain behind bars, an Italian judge ruled Saturday.

The judge rejected a lawyer's request to transfer Amanda Marie Knox, 20, of Seattle, to house arrest.

Knox is being held in Perugia in central Italy in the Nov. 1 stabbing death of 21-year-old Meredith Kercher. Knox has been jailed since Nov. 6, and judges have ruled that she can be held for up to a year while the case is investigated.

Luciano Ghirga, a lawyer for Knox, said Saturday he had sought to have her placed under house arrest, but the judge in Perugia rejected the request, Ghirga said, without elaborating.

According to the ANSA news agency, the lawyers wanted Knox moved to a shelter operated by Catholic charity Caritas. They had hoped this would persuade the judge to release Knox from jail, ANSA said.

Kercher was found dead from a stab wound to the neck in the apartment she shared with Knox in Perugia, a university town about 110 miles north of Rome. Prosecutors have said she was killed resisting a sexual assault.

Knox and two men have been jailed for months in the case, although no formal charges have been filed. All three deny wrongdoing.

The men are Knox's former Italian boyfriend, Raffaele Sollecito, and an Ivory Coast national, Rudy Hermann Guede.