The company issued a statement to tie in with Nor-Shipping in Oslo that a US owner had ordered three 115,000-dwt vessels for $330m.
There is an option attached to the contract for a fourth vessel.
TOO announced the order on Monday, saying only that a Korean yard would handle the business.
It put the price at $365m.
Delivery will be from the fourth quarter of 2017 through the first half of 2018.
