Technical issues have delayed the results of a probe into a train crash in July which killed 40 people in eastern China having originally been promised for the middle of September.
The official Xinhua news agency said the investigation into the accident near the coastal city of Wenzhou needed more time, despite more than 200 meetings and the collation of more than 1,300 documents.
The crash took place when a high-speed train rammed into one stranded on the track, apparently after being hit by lightning.
"Much basic work has been done and important basic data and test materials have been obtained," Xinhua cited the investigation team as saying.
"But there are still many technical and management issues which need further analysis and verification. The accident investigation report still needs some time to be put together," the report added.
The team will "take a rigorous, conscientiously responsible attitude and continue to keep a firm grasp on the job at hand and will not let slip any uncertain points", Xinhua said.
The team's progress and eventual results will be released publicly "in a timely manner", the report added, without giving a timeframe.
Soon after the crash, domestic media had blamed foreign technology.
But railway authorities subsequently said a signal that should have turned red after lightning hit the train that stalled, remained green, and rail staff then failed to see something was amiss.
Premier Wen Jiabao vowed that an investigation would be thorough and transparent, and several senior railway officials have been fired.
A Chinese railway research institute also took responsibility for a flaw in signalling equipment that led to the accident, a rare admission of guilt by a state body, and the authorities promised a full review of safety procedures.
The incident prompted question marks over technology promoted as a symbol of the nation's growing prowess.