Firecracker powder ignited by a cigarette engulfed a Vietnamese passenger bus in flames, killing at least 43 people, official Radio Hanoi reported.

The bus burst into flames on Saturday while waiting to cross a bridge in Thanh Hoa province south of the capital of Hanoi, the radio said. A text of Sunday's broadcast was seen in Bangkok Monday."According to initial reports, 43 people were killed and four others seriously injured," it said. "The fire was caused by a large amount of firecracker powder carried on the bus by passengers which was ignited and set off by a cigarette butt."