Staff from the Ministry of Defence are completing the final phase of a clear-up operation in woodland near Woodhall Spa, which was the scene of a mustard gas incident.
The staff are working at Roughton Moor where gas canisters - believed to date from the Second World War - were found last October.
During the work, the MoD staff will be wearing protective equipment as a precaution.
The woods have been closed to the public since the canisters were discovered by people apparently digging for antique bottles.
Two people were treated in hospital for minor burns and respiratory problems when the canisters were unearthed.
The woodland is close to the former RAF Woodhall Spa station, which functioned from 1942 until the mid 1960s.
Other military units were also based in the area during the Second World War.
East Lindsey District Council has confirmed Kirkby Lane will be closed while the work takes place.
Once the woods have been given the ‘all-clear’, the council says it will consider taking down fencing at the site and removing security guards.
• The clean up was initially due to start earlier this month but there were unconfirmed reports MoD staff had been transferred to the investigation surrounding the alleged poisoning of former spy Sergei Skripal and his daughter Yulia in Salisbury.