CSR Corp and China CNR Corp, the nation's two biggest trainmakers, suspended their stocks from trading on Monday in Hong Kong pending the release of an announcement containing inside information.

The two companies did not elaborate in their statements to the Hong Kong stock exchange. The shares were halted for trading on the Shanghai exchange as well.

Shares in CSR and China CNR had surged last month after a report that China's State-Owned Assets Supervision and Administration Commission, is seeking the merger of the two companies to boost exports of high-speed railway technologies. The plan was reported by Caixin on its website Sept 3, citing people it didn't identify. The two companies said at the time that no plans had been submitted.

"Everybody is obviously expecting CNR and CSR to announce something relating to the merger between the two companies," said Lawrence Li, a Shanghai-based analyst at UOB Kay Hian Investment Co. "But it remains to be seen what form any merger would take. Some form of collaboration might be more efficient if it is just overseas projects they are concerned about."

China CNR fell 2.3 percent to HK$7.66 ($0.98) in Hong Kong on Friday. CSR declined 0.3 percent to HK$7.89.

Zhang Yong, head of CNR's publicity department, said he had no additional information on the suspension or when the trading will resume. Two calls to CSR were not answered. SASAC did not immediately respond to a faxed request for comment.

Last week, Boston transport authorities awarded CNR a $567 million contract to supply trains for the city's subway system, the first deal of its kind for a Chinese company in the United States. CNR offered the cheapest price among five bidders and a little more than half of Bombardier Inc's bid.

Chinese rail partnership wins landmark Boston subway deal	On track for high-speed growth