A BUILD-UP of wet wipes and cooking fat led to a waste pipe being blocked in Marston.

Residents said they noticed the brook behind Arlington Drive had turned bright green on Wednesday.

Thames Water said its workers had used a green florescent dye to trace where the pipe was blocked.

Spokeswoman Becky Trotman said: “The green colouring in the brook is from an organic dye used to check the source of the water flowing into it.

“It is completely harmless and will disperse naturally.

“We needed to use it after a ball of solidified cooking fat mixed with wet wipes to block a nearby sewer. We spent yesterday clearing the blockage, assessing the brook and flushing our pipes through and the area is now back to normal.”

Martin Cox, who lives in the street, said: “It started on Wednesday morning and then by lunchtime Thames Water had arrived with three vans and several people.

“There were a few people doing other testing and looking at the brook.

“There was a strong smell of sewage and they were investigating the source.”

Mr Cox added: “They did a very good job, very quickly.”

Another resident Heather Morris added: “There were tankers here for hours.

“I do not know what was going on, but they blocked the road off. Hopefully it’s sorted now.”

Last April, Thames Water closed the Frideswide Square to remove a mass of fat and other waste – dubbed a “fatberg” – that had caused a partial collapse of the sewer.

At the time it estimated the repairs would take two weeks to complete.

Drivers were forced to wait in long queues over four days because of the road closure.