An unmanned Russian Proton-M rocket carrying three Glonass positioning satellites wobbled and veered after launch before breaking apart and crashing back down to the launch site in a fiery explosion.
There have been no reported casualties, but state news agency Ria Novosti reports that officials warn that a cloud of poisonous smoke from the rocket's fuel could spread across the area in Baikonur, Kazakhstan.
Rain was helping subdue the smoke from 600 metric tons of highly toxic heptyl, amyl and kerosene rocket fuels, but it "might" still drift toward the nearest town, nearly 40 miles away, according to the head of Kazakhstan's Emergencies Ministry, Valdimir Bozhko.
The launch was broadcast live by Rossiya-24 television, and showed the second unsuccessful launch of a Proton-M rocket with Glonass positioning satellites in the last three years. The station reported the loss of the satellites to be valued at $200 million.
The other mission failed in December 2010, when the rocket's upper-stage Briz engine failed. The partial failure of the same booster in an August 2012 launch left a payload stuck in the wrong orbit.
Work at the Baikonur space center will likely be suspended for two or three months because of contamination, a space official told RIA Novosti. The planned July 27 launch of a Progress M-20M spacecraft is likely to be delayed as well.
Though a cause for the latest launch failure has yet to be determined, the Emergencies Ministry said a near-instantaneous failure of the rocket's first stage engine was to blame.