A second person has been arrested following the discovery of mustard gas canisters near Woodhall Spa.
Police arrested a 38-year-old man from Lincoln on the evening of Tuesday, October 3 on suspicion of being in possession of a noxious substance.
A woman, also from Lincoln, was arrested on Wednesday, October 4.
No charges have been brought against the pair in question at the time of writing and both are being held for questioning.
Two people were taken to hospital for treatment to burns and minor respiratory problems after they discovered the canisters while bottle digging in the Roughton Woods area near Woodhall Spa n Sunday, October 1.
The area, known as the Ostler Plantation, has since been cordoned off by police and a major incident was declared.
Work was carried out to confirm that the woodland was a safe place and there was no further risk to people visiting and living in the area.
It is believed that the mustard gas canisters have been in situ since the site was an operational air base, formerly known as RAF Woodhall Spa.
The canisters were taken to Porton Down, the Defence Science and Technology Laboratory, where the substance was confirmed to be mustard gas.
Police are working with other emergency services, military and health partners to ensure the safety of the area and to establish if further canisters are present.