India, Oct. 4 -- The death toll from the suspected drug poisoning doubled to 12 children across Madhya Pradesh and Rajasthan on Friday, but there emerged a new mystery over what caused the fatalities after one set of officials said they found no trace of toxic contaminants in medicine samples they analysed.

The ministry of health and family welfare said laboratory tests detected neither diethylene glycol (DEG) nor ethylene glycol (EG) - industrial chemicals known to cause acute kidney injury - in cough syrup samples collected from Chhindwara district, where nine children have died since early September, up from six reported earlier this week.

Biopsy reports cited earlier this week by Chhindwara district collector Sheelendra Singh initia...