CHICAGO (CBS) — Approximately 200 firefighters battled the flames at a historic building on Jewelers Row overnight, and helped rescue two people trapped inside.

The fire started around 1:30 a.m. at the 106-year-old Mallers Building at Wabash and Madison. The 23-story building houses 180 jewelers.

Flames were shooting out a fourth floor window, and at least two men who were working late were trapped inside. They could be seen waving for help as firefighters arrived.

Firefighters rescued the two men using a ladder truck.

“We were tapping the window. It was so much smoke, we couldn’t even go in the hallway, because it’s like a lot of smoke, and smoke started coming in the place. We were all the way in the back room. We were okay for a while, then smoke started getting really heavy,” Koko Deveci said.

The blaze eventually was upgraded to a 3-11 alarm, bringing a total of about 200 firefighters to the scene.

The extra crews were brought in to help search the upper floors of the building, but no one else was found inside.

The fire was extinguished by about 3:30 a.m. Officials said the fire started on the fourth floor, which was destroyed by the blaze.

“They had a difficult time fighting the fire, because of the heavy smoke on the third floor, but once they got to the scene of the fire, they were able to put it under control. They did a phenomenal job up there. Like I said, there was zero visibility on the third, fourth floor where they were operating,” Deputy Fire Commissioner William Vogt said.

The flames spared Chuck Horberg’s jewelry shop on the 7th floor. As the longest tenant in the building, in business for 50 years, he recalled another scare at the Jewelers Center in 2002.

“Twenty-s ome-odd years ago, we had an explosion in the building. That was a butane tank blew up, but that’s the only problem we’ve ever had,” he said.

Officials said the building’s proximity to the Washington/Wabash stop on the ‘L’ did not affect firefighting efforts.

One firefighter suffered a leg injury, and another was overcome by heat, but officials said their injuries were minor.

The cause of the fire was under investigation.