LUCKNOW/AGRA/KANPUR/Gorakhpur, Dec. 17 -- Dense fog wreaked havoc across Uttar Pradesh, triggering a series of road accidents on Tuesday that left at least 26 people dead and dozens injured in eight districts. The worst tragedy unfolded in Mathura, where a massive pile-up on the Yamuna Expressway claimed 13 lives, most of them charred to death after vehicles caught fire. Eight buses and three smaller vehicles collided with each other at the 127 km milestone on the Yamuna Expressway near Baldev town in Mathura around 4.30am. The vehicles were travelling from Agra towards Gautam Buddha Nagar when visibility dropped sharply due to dense fog, said officials. SSP (Mathura) Shlok Kumar said the accident occurred when drivers failed to see vehicles ahead in near-zero visibility. "Initially, four deaths were reported. However, during a detailed search of the burnt buses, charred remains were recovered, taking the death toll to 13," he said. Several vehicles caught fire following the collision, trapping passengers inside. Fire tenders were rushed to the spot to douse the blaze, while ambulances shifted the injured to the community health centre in Baldev, later referring them to the district hospital in Mathura. "Most bodies were badly burnt, making identification difficult. DNA samples will be preserved to help families identify their kin," the SSP said, adding that an FIR is being registered in the case. Some UP Roadways buses were also involved in the pile-up. District magistrate of Mathura, Chandra Prakash Singh, ordered a magisterial inquiry into the incident. A committee headed by the ADM (administration), with the ASP (rural), executive engineer (PWD) and assistant RTO as members, has been constituted. "The committee will probe the causes of the tragedy and suggest preventive measures. It will submit its report within 48 hours," the DM said. He added that chief minister Yogi Adityanath has directed officials to ensure the best possible treatment for the injured and extend all assistance to the bereaved families. Prime Minister Narendra Modi expressed grief over the Mathura accident and announced an ex-gratia of Rs.2 lakh from the Prime Minister's National Relief Fund (PMNRF) for the next of kin of each deceased and Rs.50,000 for the injured. Chief minister Yogi Adityanath also announced compensation of Rs.2 lakh each to the families of the deceased and Rs.50,000 to the injured, directing officials to ensure speedy rescue, medical care and relief. The Mathura district administration issued helpline numbers - 0565-2403200, 2505225, 9454417512 and 9454417583 - and set up a control room to assist families. Authorities advised convoy movement on the Yamuna Expressway during dense fog and urged drivers to avoid speeding and overtaking. In another fatal accident, four people from Modinagar in Ghaziabad were killed around 6am when their car collided with another vehicle, hit the divider and overturned multiple times near Bangarmau of Unnao district. The car was completely mangled. Similarly in Basti, at least four people were killed and 18 injured when a private passenger bus carrying around 60 devotees from Sant Kabir Nagar to Ajmer Sharif collided head-on with a speeding truck near Bade Ban under Kotwali police station limits post midnight on Tuesday. Three critically injured passengers were referred to BRD Medical College, Gorakhpur. The deceased included the bus and truck drivers. In Baghpat, two persons, including a head constable, were killed when a car skidded off the Balaini bridge and plunged into the Hindon river amid dense fog. In Sitapur, a motorcyclist was killed after being hit by a truck, while another car-truck collision left five people injured, three of them critical. Meanwhile, two persons were killed and three others injured after a speeding car collided with another vehicle amid dense fog on the Purvanchal Expressway in Barabanki on Tuesday, police said. The accident occurred near Sariyan village when an MUV, attempting to overtake another vehicle, rammed into an SUV moving ahead, they said. Due to poor visibility caused by fog, the drivers of both vehicles failed to spot traffic on the expressway in time, the police said, adding that the impact was so severe that the MUV was flung into the air and fell into a roadside ditch after skidding off the road. In Lakhimpur Kheri, two students were critically injured when a truck rammed into their motorcycle while a collision between a truck and a dumper injured both drivers in Balrampur. An ambulance crashed into a closed shop in Etah due to poor visibility, leaving the driver seriously injured. Police officials said visibility plunged to less than 10 metres in at least 35 districts, including Agra, Prayagraj, Bareilly and Moradabad. In the past four days alone, more than 100 vehicles have been involved in fog-related accidents across the state, resulting in at least 31 deaths and dozens of injuries. Authorities urged commuters to avoid non-essential travel during early morning and late-night hours, drive at low speeds, use fog lights and strictly follow traffic advisories....