A confidential report by UN investigators confirmed that a "fighter jet from a foreign country carried out a deadly missile strike on the immigration detention center" in Tajoura on the evening of July 3, the BBC reported.
The BBC said the classified report did not mention the name of the country, but a source familiar with the investigation said it was focusing on the United Arab Emirates, which did not comment when the BBC tried to contact it.
The air strike, which targeted the center for illegal immigrants in Tajoura, east of the capital Tripoli, killed 53 migrants and wounded 130 others, described by the UN envoy to Libya Ghassan Salamé as a "possible war crime."
Most of those killed at the Tajura migrants' shelter were believed to be sub-Saharan Africans trying to reach Europe via Libya, the BBC said.
"This attack, depending on the circumstances, could be a war crime," said Michelle Bachelet, the UN High Commissioner for Human Rights. The United Nations Support Mission in Libya told the BBC that it had shared the coordinates of migrant centers with both sides in the conflict to prevent this type of incident.
Government forces of the National Accord said in July the attack was "carried out by a fighter plane from the UAE." The LNA, led by Marshal Khalifa Hafter, initially said it had bombed a legitimate target but later denied involvement.