Officials in a separatist rebel-held city in east Ukraine say the death toll from an accidental explosion at a coal mine has risen to 32.

The self-appointed government in Donetsk said in a statement Thursday that one person still remains unaccounted for.

The blast occurred before dawn Wednesday more than 3,200 feet underground at the Zasyadko mine in Donetsk, where bitter fighting has raged for almost a year between Russian-backed rebels and Ukrainian forces.

Rebel officials said the accident was caused by methane gas.

Zasyadko mine has a history of deadly accidents, including one in November 2007 that killed 101 workers, and two more the following month that killed a total of 57.