(CNN) -
Bulgarian authorities have launched an investigation into a passenger bus fire that left at least 45 dead and seven injured, according to state media.
After initially reporting 46 deaths, authorities now say it is unclear whether 45 or 46 people died in the incident, according to Bulgarian National Television (BNT).
Authorities believe the bus was carrying a total of 52 passengers, 12 of them children, when the fire broke out around 3 a.m. local time on Tuesday (8 p.m. ET Monday).
The bus, which had a North Macedonia license plate, was traveling on the Struma Highway, west of the capital, Sofia.
Most of the passengers were tourists from North Macedonia, authorities said.
The bus driver was among the dead, according to BNT.
The seven people who survived are in stable condition, according to BNT.
News in development
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Bulgaria