NASA engineer warned of 'catastrophic' risk to shuttle

Just two days before Columbia’s mysterious break-up during its fiery descent, a safety engineer warned by e-mail about risks of “catastrophic” failures from extreme heat causing the shuttle’s tyres to burst inside the spacecraft, Nasa has disclosed.

Meanwhile, searchers near Hemphill, Texas, about 140 miles north east of Houston, said they recovered what they believed to be one of Columbia’s tyres.