Complex sentence: Some four hundred prisoners were killed and Princess Mafalda was seriously wounded: she had been housed in a unit adjacent to the bombed factory, and when the attack occurred she was buried up to her neck in debris and suffered severe burns to her arm.
Split into simpler sentences: Some four hundred prisoners were killed and Princess Mafalda was seriously wounded. She had been housed in a unit adjacent to the bombed factory and when the attack occurred she was buried up to her neck in debris and suffered severe burns to her arm.