US warplanes have carried out 82 strikes, supporting the anti-IS ground forces.Analysts say ousting IS from Libya would be a symbolic boost for the fragile unity government, but unrest might continue as IS could carry out more scattered attacks across the country.More than 400 loyalist fighters have been killed and nearly 2,500 wounded in the battle for Sirte since May, and that figure is set to rise.
Most of the militias are from western cities backing the unity government of premier-designate Fayez al-Sarraj.
The bone pit at Sima de los Huesos is at the bottom of the cave, beneath an abrupt vertical shaft measuring between 2-4 meters (6.5-13 feet) in diameter, and located about .5 kilometers (~1/3 of a mile) in from the Cueva Mayor entrance.
That shaft extends downward approximately 13 m (42.5 ft), ending just above the Rampa ("Ramp"), a 9 m (30 ft) long linear chamber inclined about 32 degrees.
Sirte has witnessed two days of heavy fighting as IS fighters prepare to make their final stand in the hometown of former Libyan leader Muammar Gadaffi on the coast.
Militias loyal to the Tripoli-based Government of National Accord launched an offensive on Sirte more than three months ago to destroy the IS bastion which posed a threat to the country's oil supplies and threatened to expand deeper into Libya.