Indonesian police and military personnel extinguish fire in Kampar, Riau province on August 29, 2016.

Toxic haze that spread across Southeast Asia from Indonesian forest fires last year caused the deaths of about 100,000 people across the region, according to the first academic study of the health impact of the smog.

The death toll was concentrated in Indonesia, which had about 92,000 excess deaths from persistent haze that choked the region between July and October, according to researchers at Harvard and Columbia.