MEXICO CITY -- Mexico's Health Department says it has now confirmed six pregnant women have been infected in Mexico with the mosquito-borne Zika virus.

Four of those cases were in the state of Chiapas, which borders Guatemala.

The department said this week there were 80 confirmed cases of locally acquired Zika throughout Mexico as of Feb. 12.

Forty-five cases were in Chiapas and 25 in neighbouring Oaxaca state. Four were in the northern border state of Nuevo Leon.

Some believe the virus is linked to a spike in cases of babies born with abnormally small heads, or microcephaly. But there is no definitive proof it has caused the birth defects.