Police say 150 canisters of potentially deadly mustard gas have been cleared from two locations in Lincolnshire.
Officers said 140 had been recovered from Roughton Moor Woods in Woodhall Spa, while a further 10 were discovered with the help of Royal Navy divers in a nearby lake in Stixwould.
Three people were arrested on suspicion of possessing a noxious substance in connection with the find. They have since been bailed.
The canisters were first discovered on 1 October by history enthusiasts digging for vintage bottles in the woods.
Two members of the group then had to be taken to hospital to be treated for burns and minor respiratory problems.
The area was cordoned off and Royal Navy and Army bomb disposal teams used sonar equipment and drones to search for more canisters.
Sonar images released by police show a crate of mustard gas at the bottom of the lake near Stixwould, where 10 canisters were recovered.
Some 22 different agencies have since been involved in the subsequent clearing and decontamination operation.
The area around Woodhall Spa remains fenced off while work continues. Officers said there is no danger to the surrounding public.
Mustard gas, which causes serious skin burns and can be fatal, was used as a weapon during the First World War and later banned under the Geneva Protocol of 1925.
It is believed the canisters originate from an RAF base which was on the Woodhall Spa site between 1942 and the late 1960s.
Police reassured residents of the village during a packed meeting at the Petwood Hotel on Thursday (12 October).
Superintendent Phil Vickers indicated at the meeting that no further canisters were expected to be found.
Police said an investigation is launched into how and when the bottles came to be dumped in the woods and lake.