Vietnamese customs officials said Monday they seized at least a ton of elephant tusks that smugglers were attempting to take into China.

Authorities said about 221 pieces of ivory were discovered over the weekend hidden on a boat on the Ka Long River, bordering the two countries.

Officials say at least two men were detained for questioning. Authorities want to know where the tusks came from and where they were headed.

Vietnam has outlawed the hunting of its shrinking elephant population. Much of the ivory smuggled in the country comes from African countries.