CAPE CANAVERAL, Feb 1: The US space shuttle Columbia, carrying seven astronauts, broke apart in flames on Saturday as it returned to Earth from a 16-day mission.

A statement by US National Aeronautics and Space Administration (Nasa) said all seven astronauts had died.

Columbia disappeared from radar screens at 1400 GMT (7pm PST)), 16 minutes before it was due to land.

Several white trails were seen coming from bits of the shuttle over Texas, according to television images.

Nasa did not immediately confirm that the crew, who included the first Israeli astronaut, were dead. But flags were lowered to half mast at the Kennedy Space Center, where it was to land. A search was carried out across Texas for debris. Nasa warned residents not to touch anything they found as the shuttle engines use highly toxic chemicals.

Nasa headquarters said there had been no reported difficulties from the shuttle before it lost contact.

Takeoff and re-entry are the most dangerous parts of a space mission. In 42 years of US human space flight, there had never been an accident in the descent to Earth or landing. In 1986 Challenger had exploded just after takeoff.

On Friday, Nasa’s flight entry director, Leroy Cain, was asked about possible damage to the left wing of the orbiter which might have occurred on liftoff. He said analyses by Nasa engineers had shown any damage to be minor, adding: “We’re not working any concerns on the orbiter.”

VIPs were seen being led away from a grandstand near the shuttle’s landing strip by Nasa officials after reports of the disaster. In Washington, the White House flag was at half staff.

There was no possibility that Columbia could have made an emergency landing, the agency said. “I’m afraid that is not really an option at this altitude,” Nasa spokesman Kyle Herring told CNN.

But there was no immediate suspicion that terrorism was involved, Federal Bureau of Investigation spokeswoman Angela Bell said.

US President George Bush cut short a stay at the Camp David presidential retreat and returned to the White House in Washington to monitor events after the latest US space disaster.

“The president is returning to the White House so he can continue to monitor the situation from here,” a spokesman said.

The loss of Columbia, the oldest of the four US shuttles, brought back memories of the explosion of the Challenger shuttle as it took off from Cape Canaveral on Jan 28, 1986, killing all seven people on board.

The seven astronauts on board Columbia had observed a minute’s silence in their memory on Tuesday.

It was 32 months after the Challenger disaster before Nasa flew a space shuttle again. Columbia was commissioned in 1981 and was on its 28th mission. It had just returned from a major refit.

The shuttle was flying at a height of 63 kilometres from Earth, with a speed of 20,100 kilometres per hour when Nasa declared what it called “a space shuttle contingency”.

Bob Molter from Palestine, Texas, about 150km south of Dallas, told National Public Radio (NPR) how he saw the shuttle break up in the sky.

“There was a big boom that shook the house for more than a minute and I went outside because I thought there had been a train accident on the nearby line. “But there was nothing and then I looked up and saw the trails of smoke zigzagging going across the sky.”

Angela Arllotto, a tourist to Cape Canaveral from Williamsburg, Pennsylvania, said: “I was so excited to see the shuttle come down. It doesn’t seem possible.”

A Nasa spokeswoman, Catherine Watson, told NPR: “All of the flight controllers are just looking at all the data trying to figure out what happened.” Watson broke down in tears when asked whether it was possible the crew had survived.—AFP/Reuters