Three men wearing ski masks and armed with knives chased down a diamond broker in North Dallas on Wednesday afternoon and snatched his suitcase with $750,000 worth of jewels inside, police said.

The broker, whose name was not released, was not injured in the bold daylight heist, police said.

It was at least the second jewel theft in the same block along LBJ Freeway, near the Dallas North Tollway, police said.

"It's a giant building that's full of diamonds and jewelry brokers," police spokesman Senior Cpl. Kevin Janse said.

Shortly before 3 p.m., the three men blocked the broker's vehicle with their car, police said. The broker ran and the thieves chased him.

"After they got his diamonds, they sliced the tires of his car so that he couldn't chase them," Cpl. Janse said.

In last month's theft, a Garland jeweler left his car outside the building with $600,000 worth of diamonds and pearls in the trunk. When he returned an hour later, the vehicle was gone, he said.

Police found the car the next morning at a nearby apartment complex.

The jewels were gone.