The blaze, reaching 15 kilometers (9.5 miles) across, was unleashed by parts of a rocket that fell to earth on Wednesday after launch from the nearby Baikonur cosmodrome, emergency situations committee spokesman Ruslan Imankulov told AFP.
The rocket had been used to successfully launch a supply ship destined for the International Space Station (ISS), emergency services in Kazakhstan said Thursday.
Russia's space agency Roscosmos confirmed the death in a statement today, attributing it to "difficult meteorological conditions in the fallout region," which is experiencing extremely high temperatures.
Imankulov told AFP the local fire service had been notified by a citizen that a "dry grass fire" was raging around 40 km from the Kazakh steppe town of Zhezkazgan at around 1325 GMT yesterday.
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The fire broke out in "the planned fallout zone" for the Soyuz 2.1a rocket, which blasted off from Baikonur at 0920 GMT (3:20 pm), according to Imankulov. The fire was extinguished by around 2100 GMT on Wednesday, he said.
Imankulov said the two Kazakhs had been working on debris-clearing for a Russian rocket-building firm, NPO Mashinostroyeniya.
NPO Mashinostroyeniya could not be reached for comment.
The Russian-leased Baikonur cosmodrome in Kazakhstan is the main hub for launches to the ISS while Zhezkazgan is the closest major town to the site where astronauts currently land on their return from the ISS.