BALTIMORE (AP) — A massive “fatberg” made up of congealed fat, wet wipes and other waste has been named as the culprit in a sewer overflow in Baltimore.

The overflow discharged about 1.2 million gallons of sewage into the Jones Fall stream last week.

The Baltimore Sun reported Tuesday that the fatberg was discovered in a sewer main near Baltimore Penn Station.

This undated handout photo issued by Thames Water on September 12, shows a view of a fatberg inside a sewer in Whitechapel, London. British engineers say they have launched a ‘sewer war’ against a giant fat blob clogging London’s sewers. Thames Water officials said Tuesday it is likely to take three weeks to dissolve the outsize fatberg. (AP Photo)

Public works officials said the walls of a century-old 24-inch wide pipe were caked with oils, grease and congealed fats. Up to 85 percent of the pipe was clogged, blocking the flow of sewage.

The fatberg has been mostly scraped off and sent to a landfill.

In London’s sewer system, a fatberg estimated to weigh more than 140 tons was recently discovered and could take weeks to destroy.