A giant fatberg weighing "around the same as three elephants" and 170ft-long has been discovered in sewers under a prison.
United Utilities said some of its staff members discovered the "bulging build-up of fats, oil, grease and other unflushables" under HMP Manchester.
Water jets are being used to break it up, the firm said.
However, its "sheer size" meant it was likely to take until the new year to fully remove it.
Fatbergs are formed when fats, oil and grease are poured down sinks and drains and combine with items that should not be flushed down the toilet, including wet wipes, nappies, cotton buds, contact lenses and dental floss.
United Utilities said specialist jetting teams had been "blasting the blockage to break it loose, then removing some of it by hand".
It added it would visit food outlets in the area to "make sure they are not putting fats, grease and oil down their sinks".
Andrew Peet, from the firm, said the "sheer size of this great lump of lard" meant removing it would "probably carry on into the new year".