Police are looking for two unknown men who robbed a taxi driver with a knife near Kapiolani Boulevard on Saturday morning.

The driver, a 51-year-old man, picked up the men in the McCully area before taking them to a place off Kapiolani Boulevard at about 4:50 a.m., police said.

One of the men put a knife to the driver's neck and demanded money. Both men took items from the driver and fled. Police opened a first-degree robbery investigation.

The robbery comes three weeks after a 54-year-old taxi driver was stabbed and robbed in Manoa.

In that case, TheCab driver Minh Van Tran picked up two men in Makiki and took them to an upscale neighborhood in Manoa.

Courage Lee Elkshoulder, who turned himself in to police, allegedly stabbed Tran in the neck, and both men allegedly took his money and fled. Elkshoulder was indicted by a grand jury last month on charges of attempted murder and first-degree robbery.

Police are still looking for the second suspect in the robbery, a man described as being in his mid-20s, 5 feet 8 inches tall, weighing about 150 pounds, with black hair.

Tran was hospitalized but has since been released.

Several taxi drivers have been robbed at knifepoint or shot while on the job in recent years.

In July 2006 a 52-year-old taxi driver was in critical condition after being shot in the neck during a robbery. Earlier that month, TheCab van driver Manh The Nguyen was fatally shot on Tantalus.