Madrid - A judicial investigation into the August 20 air crash that killed 154 people in Madrid has begun hearing witnesses, Spanish judicial sources said Wednesday.

Judge Juan Javier Perez will hear witnesses, including a stewardess who saw the accident from another plane, and airport employees for several weeks.

The investigation moved into a new phase after a civil aviation investigating commission released a preliminary report showing that the Spanair MD-82 jetliner travelling to the Canary Islands took off without its wing flaps and slats deployed.

The plane's warning system did not go off, failing to inform the pilots of the problem.

The plane crashed immediately after take-off. Eighteen people survived Spain's worst aviation accident in 25 years.

A US judge, who is also investigating the accident, has ordered the US aircraft maker Boeing to hand over all the available technical information on the crash plane.