Any updates on type of aircraft involved, time of accident, more precise location and number of casualties?
Update: On the PPR (Professional Pilot Rumours Network), they are reporting it is a 737-800, went down near Wuzhou ( in Guangxi, near where the Xi Jiang (West River) flows to the Guangdong border to join the Pearl River), but not confirmed yet:
Before we speculate on the causes, I should say in fairness to Mainland airlines, in terms of air safety, they actually have had a pretty good record for the past 15 years or so, with relatively few incidents despite the large growing volume of air traffic. This was in contrast to the 90's, when air safety was horrid on the Mainland with frequent crashes (something which they shared with their arch-rival across the Taiwan Straits, Taiwanese airlines also had a terrible safety record). But to the credit of the mainland (give them credit where it is due), they recognized the problem and adopted US FAA procedures in flight management, aircraft maintenance and pilot training, leading to a much improved air safety record.
Of course, the pandemic and long periods of non-flying by pilots have raised questions about whether their flying skills have gone rusty.