The festival, called Chaharshanbe Suri in Farsi, is celebrated every year on the night of the last Tuesday of the Iranian calendar year, which ends on March 20.
Eleven people were killed and more than 3,500 injured during celebrations for Iran's traditional fire festival ahead of the Persian New Year.
"Since February 20, 26 people have died in incidents related to Chaharchanbe Suri," including at least 11 on the day of the event along with more than 3,550 injured, emergency services chief Jafar Miadfar told state television on Wednesday.
During the festival, participants jump over bonfires to purify themselves and ward off evil spirits, while chanting "I give you my yellow colour" (indicator of disease) and "I take your red colour" (symbol of life).
The festival is part of Iran's pre-Islamic heritage and generally frowned upon by the Shia clerical establishment.
But it is popular with young people, many of whom make their own fireworks for the event, a practice that sometimes results in injury or even death.
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