Workmen called out to clear drains in Shropshire found the blockage had been caused by what was reported as "piles of meat-eating piranhas".
Residents in Madeley, Telford had reported a fishy smell coming into their homes from the sewers, so Severn Trent Water sent a team to investigate.
One of the workmen, Matt Final, said: "We’ve certainly seen some weird things in the sewers over the years but we were a little shocked to remove piranhas.
"You wouldn’t think a fish of this size would fit down a toilet. It is just one example of amazing things we find blocking the sewers."
Some of the fish were reportedly several inches in length. It appears that a nearby resident had been disposing of dead fish down the toilet and they had blocked the sewers.
However, as keen fishkeepers will no doubt notice, the fish shown in the photo supplied by Severn Trent isn't actually a piranha, but a tilapia.
The mistake was picked up by a number of Shropshire Star readers after it ran the story on the discovery of the "meat-eating piranhas". The Guardian later asked Severn Trent if it was really sure the fish was a piranha.
A spokeswoman for Severn Trent Water said: "No, we're not. Apparently it's a tilapia, which isn't quite as exciting."
But she continued: "It scared our guys to death — they were told by a neighbour that someone had been flushing piranhas down the toilet. And you have to admit, it looks quite like a piranha."
But whatever the species of fish, the message remained the same: "At the end of the day people shouldn't be flushing fish down the toilet, it causes blockages and can make it very smelly for your neighbours."
What isn't known are the circumstances that led to one of the residents disposing of a number of dead fish down the toilet in the first place.
This is the second recent sewer blockage by unusual items in the Shropshire area this year. In January, sewers near Bridgnorth were blocked — by piles of pants!
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