All three learners from Hoër Tegniese Skool Tuine in Pretoria West who were hospitalised after smoking an unknown substance on Monday have been discharged. According to the Gauteng Department of Education, one of the learners was discharged from hospital on Monday and the other two on Wednesday.In a statement, the department added that the learners - who are in Grade 8 and 9 - have had a meeting with the school and that their parents were called in as well.Learners found having seizuresNews24 previously reported that the three teenagers, still in their school uniform, had to be rushed to Life Eugene Marais Hospital after smoking what police say is currently an unknown substance.READ: Herbal blend, puff, blazing: Pretoria school children hospitalised after smoking unknown 'drug'BestCare emergency services spokesperson Xander Loubser told News24 that the three teens were in a serious condition and were being treated for symptoms including seizures, psychosis, nausea, vomiting and hallucinations.In a video seen by News24, one of the pupils is squirming and arguing with paramedics about the drip in his arm. He can also be heard denying that he smoked anything.The teens form part of a group of 14 teens and young adults from Pretoria who have been hospitalised after smoking the substance known as herbal blend, puff or blazing or crazy coconut.South African Police Service spokesperson Captain Augustinah Selepe said the unknown substance is packaged inside a black, small bag. The substance is similar to marijuana, she added.(Supplied)"We have been informed by those who were admitted that the substance was sold in spaza shops, liquor stores, tobacco shops and even at sweet shops," Selepe said.Urgent forensic testing Police could not confirm whether the substance was a new drug that has hit the South African market. "SAPS have urgently sent the substance to a SAPS forensic lab for testing. Police have opened an inquiry waiting for forensic results," Selepe said. Police have not opened a case and have lodged an inquiry into the substance instead."If it is found that the substance is a drug then all those who are selling it will be arrested and charged for dealing in drugs," she said.Selepe said the substance was either mixed with a cigarette or rolled like a cigarette and smoked plain.ALSO READ: Alarm over cough syrup drug abuse among Cape Town learnersPretoria police and paramedics have urged parents and guardians to closely observe their children Loubser pleaded for parents to keep a close eye on their children, while Selepe said that if a suspicious substance is found, parents must remove it, report it to police and speak to their children about the dangers."They must keep an eye on them, particularly school-going children. They must regularly search their bags and other items where it could be hidden," said Loubser. "The substance is dangerous and its containers have a warning message that it is not for human consumption. Reactions for those who smoke the substance vary. Some are nauseous, some vomit and some become aggressive," he said.