GND EVAC WITHOUT INJURY.

Narrative

AS THE ACFT WAS MANEUVERED ONTO RWY 26L; IN ATL; ONE OF THE FLT ATTENDANTS RPTED SMOKE IN THE AFT CABIN. THE TWR WAS INFORMED THAT WE NEEDED TO CLR THE RWY. TWR CLRED US TO CONTINUE ACROSS THE RWY AND ONTO TXWY 'B.' THE ACFT WAS STOPPED AND ONE OF THE FLT ATTENDANTS RPTED THE SMOKE WAS GETTING THICK AND REQUESTED THE OXYGEN MASKS. AFTER RULING OUT THE PRESENCE OF FIRE; THE MASKS WERE DEPLOYED. AN EMER WAS DECLARED; THE EMER EQUIP WAS REQUESTED AND THE EVAC CHKLIST COMPLETED. I ORDERED AN EVAC THROUGH THE FORWARD-MOST DOORS (52 PAX; 7 CREW). THE EVAC WAS COMPLETED WITHOUT INJURY OR FURTHER INCIDENT. A SIGNIFICANT HYD LEAK IN THE LOWER; CENTRAL AREA OF THE FUSELAGE WAS THE CAUSE OF THIS PROB. THIS FLUID CAME IN CONTACT WITH HOT AREAS OF THE APU; VAPORIZED; AND WAS PULLED INTO THE CABIN AS VISIBLE FUMES. AFTER SHUTDOWN OF ENGS; APU; ETC; THE CONDITION STABILIZED DURING THE EVAC. THE FUMES WERE NOT ELIMINATED; HOWEVER; UNTIL AN AFT DOOR WAS LATER OPENED. SOME FLT ATTENDANTS AND PAX RPTED RELIEF FROM THE OXYGEN MASKS BRIEFLY; BEFORE MOVING FORWARD AND EXITING THE ACFT.