Vietnam spent US$19 million importing salt in 2014, a year when local sea salt harvesters were left with a huge surplus.
Experts say companies have bought cheap, mined industrial salt and sold it as sea salt suitable for kitchen use.
Their scheme has forced local farmers to keep throwing their salt back into the sea.
Figures released by the Ministry of Agriculture and Rural Development showed that salt imports in the first 11 months of 2014 increased 150,000 tons ($3 million) over the same period of 2013.
The amount was way beyond the Ministry of Industry and Trade’s limit of 102,000 tons on industrial salt imports, which are supposed to be used for chemical and medical products.
According to customs officials, several businesses have taken advantage of preferential import tariffs on industrial salt to buy a lot from overseas mines and then package it as sea salt.
An insider familiar with the matter said Vietnam’s government is considering tightening salt imports this year, so importers are hoarding as much as they can.
Meanwhile, sea salt inventories across the country rose to 200,399 tons. Farmers are waiting for a better price, or just a buyer.
Many farmers said they were offered very low prices this year – between VND800-1,200 (3.7-5.6 US cents) a kilogram, down 30 percent from last year.
Nguyen Quang Khai, deputy director of the Central Region Salt and Commerce JSC, said farmers from most coastal provinces have seen a bumper crop, but local producers haven't seen much demand from buyers.
Vietnam imports salt mostly from mines in China, or salty lakes in India and Pakistan.
That kind of salt doesn't contain essential minerals such as magnesium, calcium and potassium, which the body needs.
It can also contains traces of heavy metals.
Engineer Nguyen Dinh Binh of the Vietnam Salt Company -- a subsidiary of the state-owned Northern Food Corporation -- said using mined salt for daily meals can lead to a dangerous mineral imbalance.
“Authorities in China and Taiwan have busted many cases in which mined salt was mixed with sea salt meant for human consumption causing chronic health problems. Many businesses in Vietnam do that to pad their profits,” Binh said.
Minister of Agriculture Vu Van Tam said developed countries like the US, Japan and South Korea are seeking clean sea salt, which is abundant in Vietnam, but local farmers have not tapped the demand effectively since they produce it manually and their harvesting methods depend on the weather.
The ministry figures showed that Vietnam exports 800 and 2,000 tons of sea salt a year to the US and Japan respectively.