Police are investigating after a man threatened and robbed a taxi driver in Strathpine last night.

Preliminary investigations suggests some time after 3am, a man caught a taxi from Emily Street, Acacia Ridge.

The journey ended at Samsonvale Road at Strathpine where the male passenger attended an address in order to find someone to help him pay the fare.

When he found no one home, he pulled out a knife and threatened the male driver.

The driver managed to get out of the taxi and ran down Samsonvale Road and flagged down a passing driver to call police.

The taxi was tracked by GPS to an address in Cotton Street at Lawnton where police observed the man in a different car with a man and a woman.

He forced the woman out of the vehicle and fled the scene in the car with a male passenger.

If anyone sees a Holden Captiva with Queensland registration 068-VGQ, they should not approach it but call Triple Zero.