The government said on Wednesday that it will keep urging the MTR to speed up the replacement of old trains, after an accident this month raised concerns in some quarters about ageing trains.

Some lawmakers are worried that wear and tear was partly to blame for two sets off doors coming off a Tsuen Wan Line train at Yau Ma Tei Station on November 13.

Railway officials say the train struck a metal barrier at the side of the track that had dislodged.

The MTR Corporation bought 93 mainland-manufactured Q-Trains in 2015, to replace the British-made fleet that has been in service on several lines for more than 40 years.

Transport minister Lam Sai-hung told the Legislative Council that the first Q-Train was put into service on November 27 and another 25 of them will be in use in the next three years.

He said it would take until 2028 at the earliest for all 93 new trains to be put into service.

"I understand [Legco] members would want new trains to be put into service as soon as possible, but upon delivery, these trains have to go through very stringent testing," he said.

"I will continue to urge the MTRC to see whether there's any room for early commissioning of new trains."

Lam said that a delay in upgrading the MTR's signalling system has also caused a delay in the train changes.

Councillors also asked about two instances this month of escalator steps breaking apart at MTR stations.

Lam said the problem was caused by items such as shoes and clothing getting stuck in the steps and the MTR will look at ways to strengthen public education to stop such things from happening.