Two cousins have died and another man is in hospital after they apparently took a batch of legal highs at a house party. Dean Boswell and Stephen John were found dead in their beds the morning after they both attended a party in Pembroke Dock, West Wales. Another friend was hospitalised after falling ill from taking the same substance, believed to be a synthetic psychoactive drug. Police are now investigating the sudden death of Mr Boswell, 36, who was a builder, and his second cousin Mr John, 40, and are awaiting the results of toxicology tests. Death: Dean Boswell, left, and Stephen John, right, died after taking a legal high at a house party . Health officials have warned that legal highs are becoming stronger, leading to a rise in the number of people being hospitalised after taking them. A friend said that the three men were at a party together 10 days ago where several people took legal highs, before they returned to their separate homes. She said: 'There were a group having a good time together on Friday night and it appears Dean and Stephen took some kind of legal high which has ended up killing them. 'It is so tragic as both of them were so full of life and had everything to live for.' Mr Boswell's mother Wynfrai said that she found her son dead in his bedroom on the morning of her 59th birthday, and vowed to use his funeral this week to alert others to the dangers of drugs. 'Dean wasn't a heavy drug user - he maybe had the odd smoke,' she said. 'I suspect they thought they were invincible. Deadly: Legal highs such as mephedrone, pictured, have grown in popularity in recent years . 'It is too early to speak about all this for both families but the vicar will be saying something about drugs at the funeral. 'Something has to be done about the people who sell drugs and the deaths that are happening in the town. The family was previously struck by tragedy when Mr Boswell's sister died on Valentine's Day a few years ago. In recent years, there has been a huge surge in the number of deaths linked to legal highs. 97 people were found dead with the substances in their system in 2012, up from 12 in 2009. It means the toll has risen by eight times in three years. In around two-thirds of cases, the post-mortem examination established that the legal high was the direct cause of death. Ministers have already introduced bans on some former legal highs, including mephedrone - known as meow meow - NBOMe and Benzofury. A ban on synthetic stimulant mephedrone came into force across the UK in 2010. The drug is now a Class B substance, along with its associated compounds. The two cousins were said to be very close to one another, and as they were both avid fans of Liverpool FC they will have the club's crest on their coffins at their funerals . A spokesman for Dyfed Powys Police said: 'An investigation is ongoing into the cause of their deaths. Police are awaiting results of a toxicology test in order to establish the cause of death.' The police added: 'Police in Pembrokeshire are committed to the ongoing fight against substance misuse across the county. Enforcement activities take place regularly, but we also educate people on the risks of substance misuse. 'We want young people in particular to be informed and aware of the serious dangers of substance misuse, and encourage family and friends to look out for them by familiarising themselves with the tell-tale signs of misuse of drugs.' Anti-drug groups say that legal highs - officially known as New Psychoactive Substances - are getting stronger and more readily available. Josie Smith, from the Welsh drug testing agency Wedinos, said: 'What we have found in the past year is an increase in the strength of NPS drugs. 'They have addiction potential far higher than some of the controlled substances.' Doctors are also concerned by the effects of the drugs bought online and in so-called 'head shops'. Julia Lewis, of the Aneurin Bevan Health Board in South Wales, said: 'We are seeing increasing numbers of people going into mental health units with acute psychotic episodes after having taken some of these legal substances. 'We are hearing of quite young people having heart attacks - I treated one 17-year-old boy who'd had a small heart attack on one of these substances.' Danger: Owain Vaughan, 14, pictured with mother Jenny, was hospitalised thanks to a legal high . Three schoolboys from Glynneath in South Wales have been hospitalised after they took a legal high which they had bought over the counter. Owain Vaughan, 14, took the drug with friends and was rushed to hospital after suffering severe fits, low blood pressure, burst blood vessels in his face and violent nausea. When he came round, he insisted he had never taken drugs before but said he assumed the substance would be safe because it was legal. His mother Jennie said: 'I'm so embarrassed but people need to be aware. My boy was given a legal high and ended up in A&E. 'I had no sleep for over 24 hours and thought my baby was going to die. I don't want any other child or parent to go through this.' After his ordeal, Owain posted a message on Facebook warning his friends not to dabble with drugs which could turn out to be unsafe or even deadly.
Dean Boswell, 36, and Stephen John, 40, took drugs at a house party . Both men were found dead the next day and another friend is in hospital . Police are currently working to determine their cause of death .