Police have announced that they have discovered a further 11 boxes that may contain mustard gas following the discovery of canisters containing the toxic substance in Lincolnshire last week.
Royal Navy and Army bomb disposal teams are working with the emergency services to search Roughton Moor Woods near Woodhall Spa, Lincolnshire.
The news comes after two people suffered minor burns and had to be treated in hospital following the discovery of canisters containing the gas on 1st October.
Police said the newly discovered boxes would be examined and searches were continuing.
The canisters are believed to date back to the site's use as an RAF base
Insp Phil Baker said searches at the nearby lake in Stixwould were also ongoing.
He said a meeting would be held at Petwood Hotel on Thursday to update the public; he said:
"We can allay any fears, people can ask questions and it's just to serve as an update for those with worries and reassure people that we won't release the woods until it is safe."
The three individuals arrested in relation to the discovery of mustard gas in Woodhall Spa, Lincolnshire, have been released on police bail until October 25th.
A search at an address in Woodhall Spa has been completed and, as with the Longdales Road address, no noxious substances were found.
A police and military presence remains at locations in Woodhall Spa and Stixwould.
Police have been searching a building in the village of Woodhall Spa, that was home to a former RAF base that closed in the 1960s.
Army bomb squad officers were called in and further testing was carried out at the Porton Down military research laboratory, which specialises in chemical and biological agents.
Police believe the canisters have been at the site since it was an operational military base.
Lt Col Andy McCombie is the link between the EOD team and the police.
Three people have been arrested in connection with the discovery.
Superintendent Phil Vickers of Lincolnshire Police said they are working with emergency services and the military to reduce the risk from the materials that have been found.
"The people who found it have been exposed to it and we are ensuring they have the best possible treatment"
Mustard gas causes severe irritation to the skin, eyes, and lungs of those exposed and was used during the First World War.
Police believe the containers have been at the site since the time it was an operational military base.
Officers have said there is not thought to be any risk to the public, but advice remains not to go near areas with a police presence.