TULSA, Oklahoma - Tulsa firefighters are working to put out a business fire in the 500 block of South Rockford Avenue. They've requested additional help with the fire Tuesday afternoon.

The building is an all-metal warehouse in the Pearl District. The Tulsa Fire Department said the initial call said the building was vacant and surrounding businesses said they didn't believe a business was operating in the building.

A "for lease" sign was posted on the property.

Flames broke through the roof and firefighters are using ladder trucks to put water on the fire from a high angle. Heavy black smoke started pouring from the interior as the fire made its way deeper into the building.

Tulsa Fire Captain Stan May said his crews are rotating as they battle the fire that was called in around 1 p.m. August 15. The heat and humidity are making for brutal conditions, he said.

"It's hot out there we're having to rotate the crews quite a bit," he said. "When they finish their first bottle we'll rotate them out, cool them down, and check their vitals before we send them back in."

Several businesses in the area are bringing the firefighters cold water as they work in heavy bunker gear.

May said they don't know what is stored in the building that is creating the thick smoke. Firefighters have been able to go into at least one of the buildings that appear to be connected.

The smoke is blowing toward downtown Tulsa and can be seen for miles. The smoke does appear to be dissipating before it hits the downtown area, according to Osage SkyNews 6 HD pilot Will Kavanagh.

The building is next to Tulsa Transit, but they have not had to evacuate. Kenn Love with Superior Linen said they saw the smoke and closed up their windows, eventually evacuating their building.

Love said the fire moved very rapidly. He didn't know of any other businesses that were evacuated.

Drivers should avoid the area as several streets are blocked around the building. If you have breathing problems, you may want to stay indoors.