Scientists who have begun work cleaning up a former chemical warfare base in Cornwall say they think it is unlikely the surrounding area has been contaminated.
The full clean-up operation is expected to take seven years
The Nancekuke site, near Portreath, produced about 20 tons of the nerve gas Sarin and local residents are concerned toxic waste may have been left behind.
Scientists have been carrying out preliminary tests at the smallest of five dump sites to establish what sort of chemical substances are present.
Although clean-up staff say they believe the area is safe, the RAF has said it is taking no risks in order to protect its staff and the general public.
Nancekuke was a secret government base which operated as a small-scale chemical production and research facility between 1951 and 1976.
The base was closed in 1980 and turned into RAF Portreath.
Scientists believe debris from the laboratories which made the deadly gases, such as test tubes, may have been dumped at the first dump site which is currently being investigated.
The site has been covered with a sealed tent and members of the team carrying out the investigation have to wear protective clothing. Their health is also being closely monitored.
RAF scientist Dr Amanda Myers said: "Because we can't be entirely sure what we're going to find, we've had to apply the highest safety standards.
"That requires using a vapour containment system, which is a tent-like structure connected to four air filtration units.
The health of the clean-up staff is being closely monitored
"What they do is suck the air inside the tent, so that when we dig into the dump site, if any vapours are released, they will not be released into the atmosphere."
The current work, however, is just the start of the procedure. The dump being looked at will not actually be cleaned up until 2005.
The clean-up of all five dump sites is expected to be completed in seven years time.
The RAF has said it hopes the operation will allay the fears of local people who have for many years been concerned about Nancekuke and its legacy.
The Ministry of Defence has said all the findings from the multi-million pound project will be made available to the public.