With Chinese authorities placing the Hekou Yao Autonomous County under lockdown, it is unclear when the trucks can cross the border.
The Ministry of Industry and Trade has advised exporters to watch the border situation when making business plans to avoid losses.
Kim Thanh was one of the border gates blocked last year when China adopted a ‘zero Covid’ policy and restricted trade with Vietnam.
In another Vietnamese province, Lang Son, nearly 2,000 trucks had queued up as of Thursday to enter China.
China was Vietnam's second-largest export market for agricultural, forestry and fishery products behind the U.S., posting an export turnover of $8.4 billion in the first 11 months of last year, accounting for 19.2 percent of Vietnam’s total agricultural exports.