Barrels of a highly explosive acid once used to make bombs have been discovered alongside other hazardous chemicals at a warehouse.
Officials found 300kg of picric acid at the industrial unit near Uckfield, East Sussex.
The Uckfield News said chloroform, formaldehyde, denatured alcohol, xylene and methanol were also among the chemicals found on the site.
No-one at Acquascience, which rented the unit, was available for comment.
Wealden Council said the firm had gone into receivership.
Items discovered also include labelled NHS test pots showing patient details.
The council, which was first alerted last Friday, said it had served a formal notice ordering the warehouse's owner to remove the chemicals.
Site owner Kevin Benton said he would not comment on the chemicals for legal reasons.
He did say there had been a "massive breach" of NHS confidentiality and he had been shocked to find "a huge quantity of containers containing liquids and tissue, each bearing identification".
The council police and Ministry of Defence officials had been to the site and agreed it was safe.
A fire service spokeswoman also said the site was secure.
Neither the council nor the fire service confirmed the substances involved.
On the medical items, NHS commissioners said they were investigating what had happened.
A spokesman for High Weald Lewes Havens clinical commissioning group, said: "Once we fully understand what the situation is, we will ensure necessary action is taken."
The Environment Agency said it sent a a stop-and-remove advice and guidance letter to Acquascience Ltd on 29 September after receiving information that waste might have been deposited at an industrial unit.
A spokesman said: "We understand that Acquascience Limited is in administration, and the landowner has taken possession of the industrial unit.
"Where a company is dissolved, responsibility for removal of waste usually rests with the landowner."