Independent team that investigates the fatal break-up of the Columbia space shuttle blamed flawed practices at the US space agency for the disaster. In their final report, published on Tuesday, investigators concluded that long-standing flaws in the NASA organisation were "as much a cause" of the tragedy as technical faults. While the space shuttle was not inherently unsafe, a number of mechanical changes should be made in order to ensure safety in the short term, the report also said. The shuttle disintegrated as it re-entered the Earth's atmosphere on February 1, killing its crew of seven astronauts.