On Monday, eBay, US online auction tycoon banned worldwide sales of sorbitol after the death of a 28-year-old Italian woman who consumed a phial of the sugar substitute as part of a food allergy test.
"As a precaution, eBay has immediately cancelled all sales of sorbitol, which will remain banned pending further clarification," the company said in a statement, adding that it was cooperating fully with an investigation.
"eBay is profoundly pained by what has happened," it said in a statement.
Two other women at the clinic were taken violently ill but survived.
Italian police on Sunday seized 1,000 tons of the substance and the health ministry has warned people not to consume any sorbitol bought online.
The batch from which the dose taken by Sunna came was produced in Italy in February 2010 by US commodities giant Cargill and then shipped abroad.
"According to our internal investigation, the batch in question at the time of its dispatch (from Italy) conformed to our rigorous standards for product quality and safety," the company said in a statement.
Sorbitol, also known as glucitol, is widely used in cosmetics, medication and diet food. It also occurs naturally in fruit like apples and pears.
"There is no need for a general health alarm" on products containing sorbitol, Health Minister Renato Balduzzi told reporters on Monday.
Sunna's death has sparked wider concern in Italy over the increase in counterfeit pharmaceuticals bought online for a saving.
The ministry said it had arrested 337 people for illegal online sales of pharmaceuticals since 2005 and seized a total of 3.7 million doses.