Investigations are being carried out into whether a toxic weed has returned to a city centre car park at the rear of The Queen’s School.

Cheshire West and Chester Council (CWaC) previously liaised with Chester Race Company, who own Linenhall car park, to ensure the giant hog weed was destroyed.

But it appears to have returned.

Race company chief executive Richard Thomas has promised to investigate and make sure the dangerous weed is removed if that proves to be the case.

Contact with toxic sap from the weed, which more commonly grows near canals and rivers, can increase the sensitivity of the skin to sunlight, often leading to burns. The burns can last for several months and the skin can remain sensitive to light for many years.

The NHS says anyone who touches giant hogweed should wash the affected area with soap and water, and keep it covered. The blisters heal very slowly. If you feel unwell after contact with giant hogweed, speak to your doctor.

Maria Byrne, director of place operations at CWaC, said: “In terms of controlling giant hogweed we work closely with the Environment Agency, the Canals and Rivers Trust and any third party who have this species of weed on their site. Where the weed is reported we inspect it to confirm the species, location and quantity. It is then recorded on to a list.

“The information is passed on to our specialist contractor who undertakes the appropriate treatment to eradicate the weed.

Toxic giant hogweed appears to have returned to the rear of Linenhall car park in Chester city centre

“We have undertaken an extensive programme of surveying and treating the weed in the last two years working around the Sealand Road and River Dee areas. This has enabled us to identify and treat the species on an ongoing basis.”

What is it? - the hogweed factfile

■ A large weed with white umbrella-shaped flower head now widespread along river banks and canal towpaths

■ Can grow about 13ft (4m) high and has leaves up to 5ft (1.5m) wide

Toxic giant hogweed appears to have returned to the rear of Linenhall car park in Chester city centre

■ Poisonous sap from stem hairs can cause severe blistering which can take months to heal

■ Resembles cow parsley but has reddish-purple stem with fine spines and spotted leaf stalks

■ Can produce up to 50,000 seeds per year