Lincolnshire Police have released three people on bail following the discovery of a stockpile of mustard gas canisters near Woodhall Spa.
A man and woman from Lincoln and a man from Woodhall Spa were arrested on suspicion of being in possession of a noxious substance in connection with the find.
Specialist policing teams conducted searches at an address in Woodhall Spa and a property on Longdales Road in Lincoln. They confirmed that no noxious substances were found at either.
All three suspects have been release on police bail until October 25.
Policing teams have been joined by Royal Navy Bomb Disposal units in surveying the Roughton Woods area, where the canisters were found by bottle diggers, and Stixwould.
A police and military presence has been seen on the site, formerly known as RAF Woodhall Spa and now used by local scout groups, since the discovery on Sunday, October 1.
With the search widened to a lake in the Stixwould area, it is unclear how long the police operation will be ongoing for.
Specialist equipment and vehicles have been used in the search of the cordoned woodland and police have indicated they may require the use of a ground penetrating radar. Officials are also scouring the area by hand to ensure it is safe to reopen to the general public.
Two bottle diggers sustained minor burns and experienced respiratory problems after the canisters were disturbed. They have received treatment and are now out of hospital.