The lunchtime explosions rocked houses and broke windows for miles around, witnesses said. The China News Agency in Hong Kong said a release of nitric acid sparked the first blast. Firefighters and police rushed to the scene and were trying to control the blaze when a nearby natural gas reservoir, Shenzhen's largest, exploded.
The news agency said some 70 people, including two deputy police chiefs, were feared dead. The Red Cross hospital in Shenzhen alone had already admitted about 200 injured. A hospital spokeswoman said doctors were unavailable for comment but the report 'was believable', adding: 'Our hospital's in a crisis situation.'
A local government spokesman said rescue workers, including soldiers, police and medical staff, were at the scene in a thinly populated area in north-eastern Shenzhen, which borders Hong Kong. The government in Hong Kong said it had received a request for help in firefighting and rescue work from Shenzhen.