Singapore-bound traffic on the Causeway was crawling at noon on Wednesday, a day after police and immigration authorities said a Malaysian woman motorist managed to sneak into Singapore at the checkpoint by tailgating a vehicle.
Traffic cameras showed a jam on the Causeway on the side leading into Singapore, while traffic in the opposite direction was smooth.
At the Tuas checkpoint, traffic in both directions appeared smooth.
In a statement on Tuesday, the police and Immigration & Checkpoints Authority (ICA) said they were going to review their security systems and work processes at the checkpoints to prevent a recurrence.
The authorities said they have arrested a 27-year-old Malaysian woman who managed to drive through the Woodlands checkpoint without clearance. She managed to give police the slip for three days before she was finally stopped when she drove into the Ministry of Foreign Affairs compound on Monday.
The case prompted Deputy Prime Minister and Minister for Home Affairs Teo Chee Hean to express his "deep dissatisfaction" to the Commissioner and the Commissioner of Police about their response to what happened.