Traces of toxic substances including asbestos and lead have been found under the proposed site of temporary accommodation blocks.

Campaigners have been fighting plans for modular housing on Manford Way Park in Hainault for months and even attempted to launch a judicial review against the council, which ultimately fell through.

However, council planning documents have revealed traces of substances such as asbestos, lead and other heavy metals were discovered in the soil on site during investigations.

These toxic substances have been linked to increased levels of cancer in anyone exposed to them.

While only traces of the substances were found, investigators concluded there is a “moderate” risk to human health posed by the materials, unless mitigating action is taken before building work begins.

Residents are concerned these substances have sat undetected, even in small amounts, in the soil underneath the children’s play area that currently stands on the site.

They are concerned this has potentially exposed young children to health risks.

Les Kaye, who lives in Hainault and has campaigned with other locals to save the Manford Way Park, said: “This is pretty serious stuff. The council have blocked us all [on social media] so we can’t even ask them for clarification. We as a group are very concerned, the minute our group realise this there will be outrage.

“Is it safe for kids to be playing on the park?”

One council document discussing the site said: “Potential risks to human health, controlled waters and the built environment have been identified from potentially contaminated made ground and black-top materials.”

Another stated there were two incidents during investigations of the site when traces of asbestos were discovered.

However, the document said the levels of asbestos discovered are not considered hazardous.

It said: “This asbestos may have originated from demolition of the former pre-fabricated residential buildings that were present on the site (demolished circa 1970).

“Both samples are below the hazardous waste threshold of 0.1 per cent for asbestos so have been classified as non-hazardous.”

Lead, a poisonous heavy metal, was detected in one soil sample at a level that was deemed to pose a “moderate” risk to human health.

Investigators recommended those building on the site would need to put a hard cap layer underneath houses, roads and parking areas on site to prevent exposure.

Flammable substances, a variety of hydrocarbons, were also discovered in the soil under the site in quantities investigators said would initially appear hazardous.

But the investigators added that the fact the substances were found in soil meant they were in fact unlikely to catch fire.

Investigators categorised the risk posed to human health as a result of the findings as “moderate”, both in the case of asbestos and heavy metals.

The report documents concluded: “There is no plan for private gardens so direct contact is unlikely.

“The site layout could be designed to cap the impacted areas (i.e. the asbestos would be left in-situ and managed through an asbestos management plan), or the impacted soil could be excavated and removed offsite to an appropriate waste disposal facility.”

A spokesperson for Redbridge Council said: “It’s not unusual for there to be a risk of contamination on a brownfield site such as this, which is why we always undertake detailed investigations as standard to understand any potential impact. The report concludes no significant remediation is required but we do appreciate residents’ concerns and, as always, will have a qualified engineer on site throughout construction should unidentified contamination be discovered so that appropriate testing and action can be taken.

“The planning officers considered all of the impact of placing homes on the Manford Way land and the required tests have been carried out. In addition, the works will be completed within the building regulations guidance. It must be remembered that health centre services were sited on this open space without any issues. The council is looking forward to providing vital homes in the borough for residents who find themselves homeless and helping manage the numbers we need to send to B&B outside of Redbridge; keeping families close to their home town while we work on long term solutions for them.”