The police has "substantially completed" its investigations into the illegal strike earlier this week and will be charging a fifth SMRT bus driver from China for instigating the work stoppage.

It has also issued stern warnings to 29 other drivers, who have since had their work permits revoked, and will be repatriated by the Immigration & Checkpoints Authority (ICA) soon.

The Ministry of Home Affairs, providing an update on the incident, said in a press statement on Saturday that "baring any new developments, we do not expect further arrests or repatriations related to this illegal strike".

"The police will be issuing warnings to the others who were involved, but no further action will be taken against them and they will be allowed to remain and work in Singapore, so long as they continue to abide by our laws," added the MHA.

On Monday, 171 bus drivers from China did not show up for work.

Eighty-eight were absent the next day. On Thursday, four drivers: He Jun Ling, 32, Gao Yue Qiang, 32, Liu Xiangying, 33, and Wang Xianjie, 39, were charged with instigating the illegal strike.

The MHA said the Public Prosecutor has obtained summons earlier today for the fifth driver to be charged in court under under the Criminal Law (Temporary Provisions) Act which states that anyone who instigates and incites others to take part in a strike or lock-out shall be guilty of an offence. The Act covers strikes of workers from essential services, including public transport.

More than 20 drivers were brought to the Admiralty West Prison from their dormitories at about 9am today.

They boarded buses charted by SMRT and were ferried to the detention centre under police escort, although they were not arrested.