A major fire broke out in the cathedral in the western French city of Nantes on Saturday, blowing out stained glass windows and destroying the grand organ in the 15th-century building, officials said. Prosecutor Pierre Sennes told reporters three fires had been started at the site and authorities were treating the incident as a criminal act. He gave no other details. Dozens of firemen brought the fire under control after several hours. Smoke was still coming out of the Gothic structure after massive flames earlier engulfed the inside. The blaze comes a just over a year after a major fire at the Notre Dame cathedral in Paris, which destroyed its main spire. After two hours, emergency teams managed to contain the fire at the gothic structure, built between 15th and 19th centuries, said regional fire chief General Laurent Ferlay. Prime Minister Jean Castex said he would visit the scene later on Saturday. "I want to know what happened but first I'm going to show my solidarity with the people of Nantes," Mr Castex told reporters. President Emmanuel Macron tweeted his "support for our firefighters who are taking all the risks to save this gothic jewel". Another religious building in Nantes - the Basilica of St Donatian and St Rogatian - was struck by a fire in 2015 that destroyed three-quarters of its roof. In April last year, a fire engulfed Paris's 13th century Notre-Dame cathedral, causing its steeple to collapse and sending billowing fumes containing toxic molten lead into the air. The structure will take years to repair. Jean-Yves Burban, who runs a newsagent facing the cathedral, said he had opened his business and heard a bang at around 7.30am. He went outside to see huge flames coming from the building. "I am shook up because I've been here eight years and I see the cathedral every morning and evening," he told Reuters. "It's our cathedral and I've got tears in my eyes." It was not the first time fire has damaged the cathedral in Nantes, which is about 340 km (210 miles) south-west of Paris. It was partly destroyed during World War Two in 1944 after Allied bombings. In 1972 a fire completely ravaged its roof. It was finally rebuilt 13 years later with a concrete structure replacing the ancient wooden roof. "The fire of 1972 is in our minds, but at this stage the simulation is not comparable," Nantes Mayor Johanna Rolland told reporters. In 2015, a fire that appeared to have been caused by renovation work destroyed most of the roof of another church in Nantes, the Saint Donatien Basilica.