(CNN) At least 15 children were killed Friday when a fire broke out at a Haiti children's home run by an American religious nonprofit, police said.

The blaze took place at the Orphanage of the Church of Bible Understanding in Port Au Prince, said Jennifer Melton, Haiti's chief of child protection for UNICEF, the United Nations' children's agency.

Haiti's President Jovenel Moise tweeted Friday that he was "deeply moved" by the deaths and directed officials to "adopt urgent measures" to determine the cause of the fire.

More than a dozen children were killed at the Port Au Prince facility on Friday, police said.

Fire officials are investigating whether a burning candle started the blaze, a police official told CNN.

Melton said about 60 children survived the fire. She noted the facility is often referred as an orphanage but in Haiti they are known was children's centers.

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