Four people have died and another 30 have been hospitalised with listeria, after eating what officials suspect were recalled enoki mushrooms from the company Sung Hong Foods.

The mushrooms were recalled on Monday with the Food and Drug Administration's website claiming they may be contaminated with listeria, a deadly bacteria.

Six of those cases involved pregnant women, and there have been two reported miscarriages among them, the CDC has said.

"Do not eat, serve, or sell any recalled enoki mushrooms distributed by Sung Hong Foods, Inc," the CDC said on its website.

The enoki mushrooms in question are labelled as products of Korea, and are long and white with small caps, according to the CDC.

They were sold in clear plastic packages with green labels, in 7.05-ounce/200-gram portions.

The source of contamination is being investigated, and it is not clear whether other products might be linked to the illness.

Listeria symptoms generally start one to four weeks after eating contaminating food, and the infections can be treated with antibiotics.

Those symptoms are different for different people. Most people experience headaches, stiff necks, confusion, loss of balance, muscle aches, fever and convulsions.