For several months contractors have been excavating World War II chemical warfare residue from the army depot.

Hundreds of shells were unearthed and were judged to be empty.

But this assessment came unstuck mid afternoon on Thursday when it was believed there had been a mustard gas spill at Denis Cooke’s Salvage Yard in Inch Street where the corroded shells were being cut up for scrap.

NSW Fire Brigade personnel responded to an emergency call just before 3 pm after a forklift pierced the World War II ordinance which subsequently started leaking a ‘jelly-like substance’.

NSW Fire Brigade superintendent Ian Krimmer said the crew’s initial concerns were that the substance would pose a risk for the community.

An exclusion zone of 250 metres was established around the site and crews evacuated homes in the zone, including residents in Inch, Macaulay, Atkinson, Guy, Laidley and Donald Streets in Morts Estate.

“Two hundred and ten people were evacuated from housing and businesses around the area and moved to the Lithgow Workmens Club.

“During the night crews relayed information to the evacuated people keeping them up to date with what was happening,” Superintendent Krimmer said.

A Jones Brothers bus was engaged to pick up residents who had no transport.

Two workers at the site who were first exposed to the substance were treated by paramedics at the scene.

A Lithgow Ambulance spokesperson said they received at call at 2.55 pm.

“One of the workers (a 48 year old male) was transported to hospital in a stable condition with suspected contamination, but he was later released after the substance had been cleared.”

The spokesperson said a second 66 year old male worker was assessed at the scene but did not require transport to hospital.

Police Media reported those who came into contact with the substance suffered a burning sensation in their throat.