An unnamed individual close to the Ministry of Railways told a reporter from 21st Century Business Herald that the operating speeds on China's high-speed rail network will be reduced yet again in around September this year. The source told the newspaper that the decision was being made due to safety considerations. The report also said that three lines (Beijing-Shanghai, Tianjin-Beijing and Shanghai-Hangzhou) will be exempted from the slow-down order. In Apr this year, the newly appointed Railways Minister Sheng Guangzu announced that as of July, high-speed trains on China's main high-speed rail lines will run at 300 km/h instead of the previously announced 350 km/h.
Source
21st Century Business Herald
Google translation