content: Published on Jul 3, 2013 The Russian space agency Roskosmos, citing preliminary information, said the accident caused no damage or casualties but the crash site was immediately cordoned off and residents of nearby towns including Baikonur were told to stay indoors and keep their windows shut. Heptyl is a highly poisonous component of rocket fuel and is known to be more toxic than the chemical weapon sarin. Kazakh officials played down the immediate danger to people, saying a lot of the fuel had burned in the air but some experts suggested the fumes may find their way into drinking water. Locals said the explosion sounded like thunder and that they were not unduly concerned about their safety. "They asked us to stay indoors and not to open windows,'' said Mukhtar Umurzakov, a 46-year-old driver, who lives in the town of Kyzyl-Orda some 300 kilometres from Baikonur. "They also said you cannot release cattle out to pasture but no one paid attention."