A forced go-slow of trains comes three days after fumes flooded compartments
The MTR suffered a rush-hour failure last night when trains were forced to go slow because of a signal malfunction.
Crowds of delayed passengers formed at two of the busier stations during the incident.
The latest problem came just three days after 600 passengers had to be evacuated from a fume-filled train in Tung Chung.
Secretary for Environment, Transport and Works Sarah Liao Sau-tung said on Saturday a repeat of such a blunder was unacceptable.
Trouble struck about 6.30pm when a signal failed at the Mongkok MTR station. The malfunction forced trains heading towards Tsuen Wan to slow down.
'Journeys between Mongkok and Price Edward took between one and two minutes longer because of the failure,' an MTR spokeswoman said.
Measures were implemented at stations along the affected Tsuen Wan line to minimise the malfunction's impact on operations.
'As it happened during the rush hour, during that period crowd-control measures were implemented to ensure smooth operations at the stations,' she said.
The procedures included holding passengers back from platforms until trains had been filled and departed.
But with many people going home after work, crowds formed at the busy Mongkok and Admiralty stations as passengers were told to wait.
Police said they had not received any reports of disturbances at the stations.Normal services resumed at about 7pm after emergency repairs.
The cause of the failure was not known last night and the MTR said investigations were continuing.
Last night's incident follows the evacuation of a train on Saturday morning.
About 600 people travelling on the Tung Chung line towards Tsing Yi had to be evacuated when choking fumes caused by a malfunctioning braking system flooded compartments.
Passengers told the train operator they could smell fumes.
All the passengers got out at the Siu Ho Wan standby platform and took the next train, 10 minutes later. No one was injured in the incident.
The mishap prompted the transport chief to criticise the MTR for having 'intolerably frequent incidents', which she said was unacceptable for a system used by 2 million people every day.
There have been two other embarrassing incidents in the past two months.
A safety screen door cracked at the Jordan station on September 7, and a six-year-old mainland boy walked, unscathed, along the railway's tracks from Ngau Tau Kok station to Kowloon Bay station last month.