On the eve of the second anniversary marking the mass kidnap of more than 270 Nigerian schoolgirls by Boko Haram militants, teenage Pakistani activist Malala Yousafzai published an open letter reminding the girls’ families that the world is still hoping for their safe return.

“I write this letter with a heavy heart, knowing you have endured another year separated from your daughters,” she wrote. “I think of you every day since we first met two years ago — and join millions of people around the world in praying for the safety and swift return of your girls.”

Since Boko Haram abducted them on April 14, 2014, it’s believed they’ve been held in captivity. While more than 50 escaped shortly after being kidnapped, reports suggest the remaining girls have likely been raped, tortured, psychologically abused and forced to marry, convert to Islam and do hard labor.

In her letter, Yousafzai also urged Nigerian President Muhammadu Buhari to take more action to find and rescue the girls.

“Would a president give up the fight for his own daughter?” she asked. “These girls are just as precious to their families.”

Despite the girls’ continued missing status, Buhari told the BBC in December that he’d “technically” won the war against Boko Haram because people were going back into neighborhoods the group had taken, and that the group has been “dealt with” as an organized fighting force.