TULSA, Oklahoma - Becco Contractors Inc. employees are salvaging what they can and clearing out damaged equipment Saturday morning after an overnight fire.

Employees say most of the fire damage is at the center of the building. They also expressed their gratitude to Tulsa Firefighters for their quick response and are thankful crews made it out safely.

Two Tulsa firefighters escaped with only a minor injury after falling through the floor of a two-story building Saturday.

Assistant Chief Doug Woods, TFD, says crews responded to reports of heavy smoke coming from Becco Contractors in the 1800 block of East 15th Street just before midnight February 14, 2014.

They found the 4,000 square-foot building - on the north side of 15th Street just east of Utica - showing extremely heavy smoke but no visible flames, Woods said.

"There was zero visibility inside and immediately outside the front of the structure," Woods said.

A two-man crew from Engine 7 entered the building to attack the fire which was on the second floor.

"As they were advancing up to the second floor, they fell through the floor," Woods said. The firefighters put out a Mayday call after crashing through the second story.

"Mayday call is when one of our crews has some kind of trouble," the assistant chief said. "We have a rapid intervention team outside just for something like that. They're sent in to find the crew."

As the three-man rescue team went into the burning building, the two firefighters were already making it out, according to Woods. One of the men injured his knee slightly but was cleared to work out the rest of his shift.

The fire was under control at about 12:30 a.m. but crews remained on scene until about 3 a.m. Saturday.

The cause of the fire is still under investigation. No damage estimates were immediately available.