Musannaf Ibn Abi Shayba 18:1153

Abu Bakr narrated to us, he said: Abd al-A’la narrated to us, from Ma’mar, from al-Zuhri, that he was asked about hired workers who were hired to demolish a wall, and it collapsed upon them, and some of them died. He said: Some of them are liable to pay the blood money to others, [which is to be paid] by those who remain.