Concerns about a sewage leak have been quashed after water at a UK beach turned a murky brown.Natural Resources Wales [NRW] has confirmed the discolouration at Porthdinllaen beach in Gwynedd was in fact caused by algae. The authority investigated after swimmers expressed worry over the Bank Holiday weekend.Alarm bells about pollution were raised at the well-known beach, which is at a remote point of the Welsh coast and looks across the Irish Sea. However, Arfon Hughes, environment team leader for NRW, has said: "Our officers received reports of potential pollution at Porthdinllaen beach over the Bank Holiday weekend."Upon inspection, this was found to be a type of non-toxic algae called Phaeocystis – one of the most common bloom-forming algae in our coastal waters. The blooms can form a brown, frothy scum that is harmless and may be influenced by recent sunlight and warmer temperatures.‌"Anyone with concerns about potential pollution can report them to us by calling our 24/7 incident communication line on 0300 065 3000 or by using our online incident form."North Wales Live reports Porthdinllaen boasts a sweeping sandy bay nestled behind a headland. The beach is renowned for its iconic seaside pub, Ty Coch, which has earned its place amongst the finest beach bars in the world.READ MORE: Met Office confirms record for hottest May day broken AGAIN as temperatures hit 35CREAD MORE: 'Call 999' health alert issued as Brits warned of 30C UK heatwave 'danger'It, like beaches across the UK, was very busy over the Bank Holiday weekend, during which temperatures in the UK exceeded 34C. The warmest places on Tuesday have already been confirmed as Heathrow Airport and Kew Gardens in west and southwest London respectively.‌But the weather is set to change as thunderstorms are forecast for parts of the Midlands, Home Counties and northern England. The Met Office says: "There is a small chance that homes and businesses could be flooded quickly, with damage to some buildings from floodwater, lightning strikes, hail or strong winds."We reported last week how residents in Plymouth have been living amongst a "horrible smell". Locals claim it's worsening, with a particular event last month being "absolutely disgusting". Some families in the Devon city have even been forced to keep their windows firmly shut to escape the stench. This grim situation is due to pollution, following a "spill" at a nearby sewage overflow.