AUSTIN, Texas — Researchers say drug overdoses were the leading cause of maternal deaths in Texas between 2012 and 2015, with opioids to blame for the majority of those.

A report Monday by a state task force blamed 64 maternal deaths occurring up to a year after giving birth on overdoses from 2012-2015, or 17 percent of total deaths. Opioids caused 58 percent of them.

A 2016 study found that Texas' maternal morality rate more than doubled between 2010 and 2012, becoming the highest in the developed world. But state researchers have since said that miscalculations inflated those previous findings.

The task force logged 382 maternal deaths from 2012 to 2015, finding that 38 percent were pregnancy related and 56 percent were associated with pregnancy.

Cardiac events caused 55 deaths and infection/sepsis 32.