President Halimah Yacob, Prime Minister Lee Hsien Loong and Foreign Minister Vivian Balakrishnan have expressed their condolences to Chinese leaders in the wake of the China Eastern Airlines MU5735 crash, the State Department (MFA) said on Friday (March 25).

In a letter to Chinese President Xi Jinping, Madame Halimah said she was "deeply saddened" and expressed "sincere condolences to the Chinese people at this difficult time" for the Singaporeans.

"Our thoughts are with the families and loved ones of those who took part in this tragedy," he said.

A plane with 132 people on board crashed in the mountains of southern Guangxi, China, on Monday as it flew from Kunming to Guangzhou after a sudden drop in altitude.

No survivors were found until search and rescue operations began on the fourth day. Rescuers found the first of two black boxes on Wednesday. The device, a voice recorder in the cockpit of the plane, has already been sent to Beijing. According to the official Chinese news agency Xinhua, the second black box has not yet been found.

In his letter to Chinese Prime Minister Li Qichiang, Mr Lee expressed "deep sadness" over the accident and expressed "deep condolences" to families and close passengers on the run from the Singapore government.

"Our thoughts are with them and with the people of China at this time of mourning," he said. Dr Balakrishnan also expressed his "sincere condolences" in a letter to Chinese Foreign Minister and Foreign Minister Wang Yi.

"I express my condolences to the affected families and to those who lost their loved ones in the escape," he said.

The Ministry of Foreign Affairs said on Tuesday that it was closely monitoring the accident situation and was in contact with the Chinese authorities.

A State Department spokesman also said they had addressed "Singaporeans in Yunnan and Guangzhou who had registered with the Ministry of Foreign Affairs," adding that there were no reports of Singaporeans on board the flight.