The countdown was perfect, the lift-off smooth. But on its maiden flight, India's most powerful intermediate-range ballistic missile, the Agni-III crashed off the Orissa coast on Sunday.

Officially, the defence ministry and the Defence Research Development Organisation say the mission team are analysing details of the disaster and the technical data will be released within a week.

But since Sunday, M Natarajan, the scientific advisor to Defence Minister Pranab Mukherjee, Atomic Energy Commission Chairman Anil Kakodkar and a number of top scientists from various DRDO laboratories have been debating why the missile failed.

DRDO officials who have worked on the project said a design failure is to blame.

"The non-separation of the first stage from the second stage was the main reason for the disaster," a senior DRDO engineer working at a Hyderabad laboratory told rediff.com on Monday. "The first stage and the second stage did not separate because of a flaw in the design," the official added.

He said the missile lifted off at 11.03 am took place as planned. "But the stage two missile could not sustain and crashed into the sea. The missile was then at a height of 12 km. To be frank, the missile launch did not meet all the strict requirements that are generally associated with a mission like this," he said, on condition that he would not be identified for this report.

DRDO sources said another reason was that a variety of new technologies that are part of Agni-III -- like rocket motors with a burn duration of more than 100 seconds, fault tolerant avionics and launch control systems -- were perhaps not perfectly integrated.

Though the mission team had tested the velocity of the vehicle, which is capable of flying at 16 to 17 times the speed of sound, sources insist the testing could not have been perfect.

Why did the DRDO go ahead with the missile test if its engineers felt the design was not perfect and the launch did not meet all requirements?

Officials say the long delay in test-firing Agni-III was eroding DRDO's image, and the pressure to test-fire the missile may have been a reason.

DRDO: An Investigation

The indigenously made Agni-III -- which has a range of about 3,500 km and is meant to carry nuclear warheads weighing up to 48 tonnes -- was scheduled to be launched in 2000. The launch was postponed first to 2003-2004, and then further, due to technical snags.

Despite Sunday's crash, Agni-III -- part of India's Integrated Guided Missile Development Programme that DRDO has embarked on -- remains the mainstay of the country's credible nuclear deterrence programme, and can target areas as far as northern China.

Agni, Agni-I and Agni-II have already undergone several test flights.

Agni-II remains the country's most proven missile. Some DRDO officials are miffed at what they feel is the unnecessarily hasty development of Agni-III instead of mass producing the Agni-II.

Given Sunday's crash, Agni-III could take years to be ready for mass production.