Norwegian Prime Minister Erna Solberg said she\'s concerned about two teenage girls who haven\'t been seen since they left Norway last week for Syria. The 16- and 19-year-old sisters, whose names weren\'t reported, sent their father an email last week explaining they were going to Syria to work in a refugee camp. The girls\' father traveled to Turkey hoping to stop them before they crossed the border into Syria, Norway\'s NRK reported. \"In my opinion this a matter of deep concern, both the danger these sisters subject themselves to, and the contacts that they make in Syria,\" Solberg said. \"Syria is not a place to be for two girls at the age of 16 and 19, no matter how idealistic they are. I completely understand that the parents are worried.\" Solberg said there is a great risk of terror for people when they return home after participating in a war such as Syria\'s. The girls may make extremist contacts while in Syria, she said.