Three sisters murdered in Gaza on Sunday were all found to be virgins by medical examiners at Al-Shifah Hospital in Gaza City, Mona El-Shawa, director of the Women's Rights Unit at the Palestinian Center for Human Rights told The Jerusalem Post Monday. Nahed Hija, 16, Suha Hija, 19, and Lina Hija, 22, were found buried in a shallow grave in Deir el-Balah in the central Gaza Strip early Sunday morning, said Hamdi Shakkour of the Palestinian Center for Human Rights. The girls had suffered multiple stab wounds - most notably to the face and knees. Local rumors implicated the sisters' male cousins in the murder, leading to speculation that this was more than likely an honor killing. Hamas authorities have released a statement saying they knew who the killers were and planned to arrest them. While at least 12 women were victims of honor killings in the West Bank and Gaza Strip last year, this was the first time three sisters were murdered together. According to Shakkour, the Palestinian judiciary does not take honor killings seriously. Perpetrators are often given light sentences of a few years, while those convicted of murder under other circumstances are sentenced to death. AP contributed to this report.