AN alert taxi driver who witnessed a robbery helped police nabbed one of the suspects by noting down the registration number of the getaway vehicle.

Mr Choo Lye Seng, 53, was picking up passengers along Orchard Boulevard on Wednesday morning when he heard shouts of 'robbery' and saw two men fleeing in a vehicle.

The alert cabby noted down the registration number of the vehicle and contacted the police.

The two men and an accomplices had earlier robbed a 20-year-old Chinese woman of her carrier bag containing various currencies amounting to about $17,000.

With the information, police managed to track down the vehicle at Ang Mo Kio Industrial Park 2.

A search was conducted on the driver who had some $3,000 worth of loot.

The 22-year-old driver was arrested for his part in the robbery and will be charged on Friday for snatch theft.

He faces a maximum jail term of seven years.

Police are still on the look out three others involved in the robbery.