The Bithumb cryptocurrency exchange Thursday advised investors to be careful in investing the listed three firms—ROM, DACC, and AMO.

In its public disclosure, the three firms would be put on a careful watch list for investment for the next month. One month later, the exchange would decide whether to delist them or free them from an investment watch list.

When companies have low liquidity, when their prices fell significantly and when the companies are implicated in a criminal investigation, the exchange put them on a watch list.