The US space agency NASA says it has lost contact with the space shuttle Columbia. Seven astronauts are on board.
Minutes before a scheduled landing contact radar and communication was lost as it crossed over Texas. It was due to land at 2.17 p.m. (Irish time). Contact was lost just 2.01 p.m.
Experts fear the worst as television picture appear to show parts falling off the shuttle as it flew across the Texas sky.
Trails of what appears to be flames are being shown by a Texas TV station streaming from the craft. It was flying at 200,000 feet at the time, moving at 12,500 miles per hour.
NASA is acting on the presumption that the craft and its crew have been lost. There is no possibility the shuttle could have made a successful emergency landing from the high altitude at which it was traveling when it lost contact with NASA, the agency said.
A White House spokesman said President George W Bush had cut short his stay at the Camp David retreat and would monitor the shuttle disapperance from the White House.
"The president is returning to the White House so he cancontinue to monitor the situation from here," Mr Scott McClellan said, adding: "We are continuing to monitor the situation and awaiting more information from NASA."
Rescue units have been scrambled in Texas and locals have been told not to touch any debris they may find.
Columbiais NASA's oldest shuttle and first flew in 1981. Today's incident is the most serious involving a shuttle since the 1986 crash of the Challenger, which carried seven astronauts.