The blast occurred in the early afternoon in the western village of Jankow Przygodzki. TVN24 footage showed yellow flames and black smoke billowing above the village's rooftops and some houses on fire. They were still burning hours after the blast.
Andrzej Borowiak, a spokesman for the Poznan police, initially said three people were killed but later confirmed firefighters' figure of two dead. He said 13 others were injured but could not confirm a report by the firefighters' spokesman, Pawel Fratczak, that two people were missing.
One adult and one child were in serious condition, according to a hospital in Ostrow Wielkopolski.
Fratczak said an existing pipeline was probably damaged while a new pipeline was being installed next to it.
The damaged pipeline was closed, but gas still trapped in it was flowing out and burning up under the supervision of firefighters. Some 12 houses burned down, he said.
Malgorzata Polkowska, a spokeswoman for the Gaz-System S.A. pipeline operator, called it "a very large-scale tragedy" and said it was the first such accident since the company was founded in 2004.
A special commission will determine the cause of the explosion.
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