A teenage boy was left 'lifeless' after swimming in a 'contaminated' pool next to a derelict Victorian paper mill.
Billy Smith, 14, had to spend 24 hours in hospital on a drip after being struck by sickness, diarrhoea and developing strange blisters on his face.
The teen and his pals fell ill after swimming in a water pool next to an abandoned Rishton Paper Mil in Blackburn, Lancs.
His mother Jo Smith, 36, has now warned of the dangers of swimming in water outside after she described how Billy was left "seriously ill'.
Jo urged other teenagers to avoid taking swims in similar waters during the summer months to cool off during the hot weather as she fears the water was contaminated.
Billy was kept in hospital for 24 hours and was only allowed home when he could keep more than 2ml of water down.
And Jo says all of his friends who were jumping in the water have also since experienced similar symptoms including vomiting, diarrhoea and skin sores.
The mother-of-one said: "He was lifeless and rolling his eyes all over the place.
"He was kept in until he could drink himself and keep the fluids in. He couldn't keep 2ml of water down.
"He could drink it, but just came straight back. He asked me if he was dying, so he must have felt awful."
Billy fell ill on Sunday, June 28, and was taken to hospital as he could not eat or drink the following day.
Jo added: "It's hard to say what has caused them to become ill.
"We had heavy floods and thunderstorms, but who knows what waste products could be flowing through.
"It could be anything from animal waste, to chemicals, we may never find out.
"I've spoken to Public Health England this morning, who have sent tests off.
"Hopefully with the recent rain, whatever it was has been diluted or dispersed. The results should hopefully be back in a few days.
"It is pretty dirty and it has been called the River Stink at times.
"But the three including Billy who went in the water have been sick and had to go to the doctors."
Now Jo wants parents of teenagers to heed her message and inform them of the dangers of jumping into water.
She added: "All the kids go in the water and even I used to do it.
"It could have been so much worse if they could not have found out what was wrong.
"Children are children and teenagers are teenagers and they will go in the water if they want to.
"But if we can tell the parents and young people about what the consequences could be then we can try to stop people getting ill.
"I've told Billy many a time that you just don't know what is underneath you at places like this."
Health chiefs in the area have launched an investigation and warned against swimming at the beauty spot.
Lancashire County Council and the Environment Agency said they are looking into "a potential issue" with the water at Rishton Paper Mill.
On Saturday, a week after the incident, Public Health England North West and Hyndburn Council issued a joint statement that read: "We have reports of children becoming ill after swimming in the water and would advise people not to enter the water.
"If you have been in this water and develop sickness or diarrhoea, fever or abdominal pain within 10 days of swimming contact your GP."