Train operator SMRT could face possible sanctions by the Land Transport Authority (LTA) for allowing the use of its trains for private purposes.

Anglo-Chinese School (Independent) yesterday chartered five MRT trains to ferry its students, staff and alumni to the Schools National C Division rugby final at the Singapore Sports Hub - the first schools final at the new National Stadium.

An LTA spokesman yesterday said: "Under the Circle Line licence, SMRT has to seek LTA's prior approval for the provision of train services that are not open to the general commuting public. In this case, SMRT did not seek our approval before agreeing to provide the service. We are looking into the appropriate action to take.

"We have also reminded SMRT that its primary focus must be to ensure good service delivery to the commuting public at large."

In response, SMRT said chartered trains run between normal train services and strictly within off-peak hours. "SMRT assures passengers that train intervals are maintained at normal service levels at all times."

SMRT had on Monday said that it had previously worked with schools to charter trains and transport students for large-scale events such as National Day Parade rehearsals.

From 1pm yesterday, about 3,000 members of the ACS(I) family boarded the trains from one-north station to Stadium station, where their rugby team beat St Andrew's Secondary 28-8 in the final.

Pictures of the trip were posted on social media. While many praised the innovative idea, some netizens slammed the decision to allow public transport to be used for private purposes.