A Shenzhen police officer checks a stroller used for smuggling foreign coins and bank notes. [Photo/chinadaily.com.cn]

Police have seized more than 4 metric tons of smuggled foreign coins and bank notes after raiding a warehouse in Shenzhen.

The haul included currencies from more than 38 countries and regions across Asia, Europe, North America, Africa and Oceania, the city’s border police force said on Wednesday.

It’s the largest case ever cracked by the force in its three-decade history.

Police received a tipoff about a currency smuggling operation in July and set up a task force to investigate.

On Aug 28, officers raided a warehouse in Shenzhen’s Luohu district and discovered more than 1 million bank notes and 1.32 million coins.

Suspects detained at the scene said the currency was being packaged and sold to collectors for huge profits, according to police.

Shenzhen is in Guangdong province on the boarder with Hong Kong.