Two out of nine electric cigarette brands sold in Japan contained a cancer-causing chemical that exceeded the level contained in normal cigarettes, according to a study funded by the country’s health ministry.

The smoke produced by the e-cigarette products, whose names weren’t disclosed, had as much as 120 micrograms of formaldehyde, compared with 76 micrograms found in cigarettes, according the study presented by Naoki Kunugida, a researcher from the National Institute of Public Health, to a ministry panel in Tokyo today.

The Japanese study comes as researchers globally debate the health effects of e-cigarettes. An article in the New England Journal of Medicine in January said formaldehyde-releasing agents can form during the e-cigarette vaping process that creates an aerosol for users to breathe in.

The agents form when propylene glycol and glycerol, typically found in e-cigarette liquids, are heated at the high voltage available on the battery-operated products.