The American space shuttle Columbia, which blasted off on January 16 from Cape Canaveral, Florida, exploded over Texas at around 1930 IST (0900 EST).

All the astronauts on board, including Indian American Kalpana Chawla, were killed.

The explosion occurred as the Columbia was re-entering the earth's atmosphere.

A National Aeronautics and Space Administration spokesperson said, "It is highly unlikely they [the astronauts] would have survived... they were travelling at a speed... They were on track, on their landing profile. There was no indication of trouble."

Besides Chawla, there were six astronauts on board, including an Israeli Air Force colonel, the first Israeli to go into space.

Eyewitnesses reported falling debris over north-central Texas. They also claimed to have heard explosions.

The NASA spokesperson said the last communication the ground crew had with the Columbia was around 0800 EST. It was a routine communication, she said, about the landing profile.

The Columbia was too far away to make an emergency landing, she added.

Chawla was the Columbia's space engineer. This was her second voyage into space.

The shuttle was on a research mission, and was launched from the Kennedy Space Centre at 1039 EST (2119 IST) amidst tight security cover in near-perfect weather.