Emergency services have been unable to access the site of a fire in Leamington Spa to search for a man who is missing.

The blaze at the plastics manufacturer Leeson Polyurethanes on Friday, which caused explosions and a huge plume of black smoke, led to the evacuation of nearby homes.

Warwickshire police said emergency workers had still not been able to enter the site and a specialist search operation would commence as soon as it was safe. They added it would be “a very thorough and complex operation which may take a number of days to complete”.

The force said it would not be possible to determine the cause of the fire until the site can be examined by investigators. The family of the missing person, who was a worker at the factory, were being kept informed, police added.

The Rosalind Franklin laboratory, a first-of-its-kind facility that opened in July and receives thousands of Covid-19 test samples a day, is situated next to the scene of the fire and was also evacuated. Tests are being assessed to see if they were affected or damaged by fumes from the fire.

Public Health England (PHE) on Monday advised local people to practice caution when dealing with soot and debris from the fire that spread over a wide area of the town. It said although toxins from plastics should have been eliminated as they burned, ash and soot particles could still irritate and rubber gloves should be worn when dealing with debris.

People were initially told not to touch any debris from the fire, but police later said agencies were struggling to clear it due to the size of the area affected.

PHE said it did not expect “a significant risk from short-term contact with soot in gardens”. It advised soot be washed off vehicles and outdoor furniture, and said fruit and vegetables grown in gardens should be washed and peeled before being eaten.

Photos showed the huge scale of the fire on the industrial estate on Juno Drive, which took firefighters 24 hours to get under control. Local media reported cases of people vomiting from the effects of the fumes.

Warwickshire police said they were working closely with fire investigators and the Health and Safety Executive, and more updates would be provided in the coming days.