BEIJING (AFP) - Two vehicles carrying explosives detonated in southwest China on Tuesday, killing at least seven people, seriously injuring 20 and causing several nearby buildings to collapse, local authorities said. The death toll was confirmed to AFP by telephone, by a spokesman from the propaganda bureau in Fuquan city in Guizhou province, where the explosion took place. A total of 225 people were taken to hospital, about 20 with serious injuries, according to a statement on the Guizhou province website. Authorities and state media have not provided further details on the cause of the explosion, which occurred around midday (0400 GMT) at an auto repair workshop on a highway in Fuquan city. The two vehicles were transporting 70 tonnes of explosives, state media reported. Houses collapse in quake: A moderate earthquake in remote northwestern China has destroyed dozens of houses and damaged many more, but there have been no reported casualties, government officials and state media said Tuesday. More than 50 houses collapsed and hundreds of homes were damaged after the 5.4-magnitude quake jolted the border area of Yining and Gongliu counties in Xinjiang, the local earthquake bureau said on its official microblog. The quake, which the US Geological Survey revised down to 5.4 from an initial reading of 6.0, struck at 8:21am (0021 GMT) around 96 kilometres (59 miles) east of the city of Yining, at a depth of 27 kilometres. The China Earthquake Administration said the quake was believed to have caused "major damage" and "strong shaking" was felt in neighbouring counties, the official Xinhua news agency reported. A special working group had been dispatched to the area to assess the damage and coordinate relief efforts, it added. Xinjiang is a vast region with a population of around 20 million, of which roughly nine million are Uighurs, a Turkic-speaking mainly Muslim ethnic minority. A 5.2-magnitude earthquake struck the region in August, injuring at least 26 people, three of them critically, and destroying more than 30 residential buildings. Earlier on Tuesday, another moderate earthquake measuring 5.5 hit the Sichuan-Gansu border area in China's southwest, a region devastated by an 8.0-magnitude quake in 2008. An official in Qingchuan county in Sichuan province, where the quake struck at 05:58 am (2158 GMT), told AFP: "It is not very serious". Another official said the quake had cracked walls and dislodged roof tiles in mountain areas but there had been no reports of casualties or economic losses.