HYDERABAD, India -- The death toll from Monday's massive explosion and fire at a pharmaceutical factory in India’s southern state of Telangana has risen to at least 36 while about three dozen were left injured, authorities said Tuesday.

It was not immediately clear what led to the blast at a factory near Hyderabad, but officials said initial clues suggested a pressure buildup in a dryer system.

India is home to some of the world's top pharmaceutical companies, playing a pivotal role in the global supply of generic medicines and vaccines.