Local data shows 4,550 trucks were queuing as of Thursday morning.
The delay in clearance is due to Chinese authorities having tightened Covid-19 safety measures. They also reported technical difficulties in their network system, said Hoang Khanh Duy, deputy head of Dong Dang Economic Zone in Lang Son.
Delays in clearance in other localities, including Quang Ninh and Cao Bang, and stoppage in Lao Cai, force most trucks to pour into Lang Son, he said.
“We are trying our best to negotiate with Chinese authorities to increase clearance speed.”