TULSA, Oklahoma - Tulsa Fire Department said the three firefighters, who remain in the hospital after a fire at a Tulsa school, are now listed in good condition.

The three had third-degree burns and needed skin grafts.

It was reported last weekend that one of the firefighters had been released from the hospital. He returned the hospital Monday and was re-admitted after it was determined that he needed skin grafts.

They've been receiving treatment in the burn center of a Tulsa area hospital since last Wednesday's fire at the Tulsa School of Arts and Sciences.

The fire department said they are improving, but there's no timetable for their release from the hospital or their return to duty.

The cause of the fire hasn't been announced yet, but the Fire Marshal's office says its investigation should be finished by Friday, when the ATF and Tulsa Fire investigators will issue their final report.