CAP-HAITIEN, Haiti, Dec 14 (Reuters) - Haitian Prime Minister Ariel Henry on Tuesday traveled to the country"s second-largest city Cap-Haitien to meet with victims of a fuel truck explosion that killed at least 50 people during the night. The truck flipped over as it was seeking to avoid running over a motorcycle, an official told local media, adding that residents initially scrambled to collect fuel from the accident - likely in response to a spate of severe fuel shortages. "I am about to go, in Cap-Haitien, to the bedside of our compatriots who were victims of last night"s tragedy," Henry wrote on Twitter. "I will take this opportunity to express my solidarity with the grieving families." He said two campaign hospitals were being set up to attend to the injured, and that three days of mourning had been declared. United Nations children"s agency UNICEF said it was working with the government to send six emergency medical kits to Cap-Haitien"s two hospitals to help with the treatment of burns. "The situation is critical because there are already about 50 dead bodies," Cap-Haitien Mayor Yvrose Pierre told Reuters. "We need human resources, and also material resources, namely serum, gauze, and anything that can be used in case of serious burns." Haitian newspaper Le Nouvelliste quoted Patrick Almonor of the Cap-Haitien municipal commission saying "Local residents were flocking to the truck when the explosion occurred." A coalition of gangs blockaded fuel terminals for nearly a month starting in October, leading to widespread shortages of gasoline and diesel that forced many businesses to close. Fuel deliveries resumed last month. As rescue workers cleaned up in the aftermath of the explosion, bodies covered in white sheets lay on the ground before they were loaded on to trucks to be taken away. The blast also damaged the fronts of houses and shops in the street and charred motorbikes and cars. Gangs have grown more powerful since the July assassination of President Jovenel Moise, which created a political vacuum and allowed criminal groups to expand their territory.