The Environment Agency is investigating reports of odours coming from the toxic old Coalite site.
Work started in November to clean up the former chemical works facility off Buttermilk Lane, Shuttlewood.
Eventually, more than 650 new homes, community facilities and a primary school could be built at the site under plans which promise to create 1,500 jobs.
But during the course of remediation work – which has included the emptying, cleaning and purging of tanks and pipelines – residents have raised concerns about nasty smells.
An Environment Agency spokesman said this afternoon: "We are investigating reports of odour coming from the former Coalite site.
"The Environment Agency's role is to regulate the excavation and treatment of contaminated land at the site to ensure that the development does not pose a risk of harm to the environment or local communities.
"Some odour is likely while the work is taking place – but the operator is required to monitor air quality and manage their activities to limit and mitigate risks to the local environment.
"Our officers have been out to assess activities at the site and we are working with the operator to identify and advise on preventative measures.
"Anyone who witnesses any pollution in relation to this site is urged to report the matter to our incident hotline on 0800 807060 so we can investigate."
A Bolsover District Council spokesman added: "We are aware of the odours coming from the former Coalite site which can vary in strength depending upon the weather conditions.
"Our environmental health department has been on the site with the contractors and are in regular discussions with the Health and Safety Executive and are continually monitoring the situation."
Scores of residents have taken to Facebook to complain of smells coming from the site.
Commenting on our Facebook page, a reader said: "The smell is getting worse."