Blackmail letters, signed 'The Terminator', were sent to the Budgen supermarket chain with demands for up to pounds 300,000.
Northamptonshire police, lifting a month-long news blackout on the investigation, reassured the public that there was 'no evidence whatsoever' that the threats had been carried out.
An investigation was launched after the first of a series of letters was sent to Budgen's distribution centre at Wellingborough, Northamptonshire, last month. A second arrived shortly afterwards.
The blackmailer claimed to have contaminated a non-food product at one store - not with the Aids virus but to prove he could do it. The named branch was checked but no contamination was found, police said.
A few days later a third letter was sent to a national newspaper threatening to target all 100 Budgen stores. It claimed goods at nine shops were already contaminated by HIV and increased the pounds 250,000 blackmail demand to pounds 300,000.
Budgen said checks were carried out daily at all stores, with staff removing products showing the slightest damage to packaging.
David Wyrko, Northamptonshire assistant chief constable, said yesterday: 'We have always had to balance the public interest against the need to catch the perpetrator of this crime.'
Police did not regard the public to have been at risk.
'So far as we are aware there has been no further contact from the person who calls him or herself 'The Terminator' and it remains the case that there is no evidence whatsoever that the threats made by that person have been carried through,' he said.
Budgen said yesterday that it had set up a hotline for customers who wanted reassurance and advice.
John von Spreckelsen, Budgen's chief executive, said: 'The Department of Health has stated that the risk of infection from contamination in this way is extremely remote . . . We are sure there has been and is now no risk to any of our customers or staff.'