Reports have surfaced claiming that microcephaly, or an abnormal condition characterizing small heads in newborns in Brazil, is not caused by Zika virus but by larvicides.

The claim was started by an Argentina-based group Physicians in the Crop-Sprayed Villages. The group released a report last week stating that the chemical larvicide called pyriproxyfen has been largely used in areas where most people fall sick. Additionally, the report claims that the same chemical was applied to the drinking water supply in the area.

The group insisted that cases of microcephaly found in that specific area where there is high exposure to the larvicide is not a result of a coincidence. The claims have prompted some Brazilian officials at South of Rio Grande to stop the use of pyriproxyfen over the weekend.

However, some scientists together with the Brazilian Ministry of Health shot down those allegations, stating that there are no scientific data backing the group's claims.

The Ministry of Health said in a statement that the association found between microcephaly and Zika virus has been confirmed in different laboratory tests, while the new claims don't have scientific basis.

Dr. Ian Musgrave, a pharmacologist and toxicologist at the University of Adelaide in Australia also gave his explanation as to why the relationship between the larvicide and microcephaly is "simply not plausible."

"Pyriproxyfen acts by interfering with the hormonal control growth cycle of insects from hatching, to larvae, to pupa. This hormone control system does not exist in organisms with backbones, such as humans, and pyriproxyfen has very low toxicity in mammals as a result," Musgrave said.

Musgrave further explained that if indeed the waters have been sprayed with the larvicide as stated in the claims, a person would need to drink more than "1,000 litres of water a day, every day, to achieve the threshold toxicity levels seen in animals."

Although several research studies have made a connection between microcephaly and Zika virus, scientists admit that more studies need to be conducted.