Two bodies have been discovered at the Ferroli facility in Branston, Burton upon Trent, after a sealed container was opened.
Police were called immediately and a forensic investigation is now under way.
The container was opened by staff concerned by the smell and the results of an autopsy are expected to be released in the near future.
Chief inspector Steve Maskrey was quoted by the Burton Mail as saying: “It is a potential crime scene.
“There is not much more we can say, but there is an investigation ongoing and we will know more when the post-mortem examinations are carried out tomorrow.”
The bodies were in a wooden transit crate containing commercial boilers, according to the BBC, which had arrived from northern Italy in Dover on 8 October before being transported to Branston.
Detective chief inspector Dave Giles told the BBC the men had been dead for some time: “We are almost certain they were helped to conceal themselves among the delivery load by a third party.
“In view of this we are treating the deaths as suspicious and will be carrying out a thorough investigation into the circumstances.”
A spokesperson for the company said: “Ferroli is fully supporting and cooperating with the police to help them with their investigation into this very unfortunate situation.”