The US Federal Maritime Commission (FMC) is expanding its probe into liner operators and their practices while roping in five more.

The regulator announced on Monday that it would begin examining how liners serve US exporters as part of its Vessel-Operating Common Carrier Audit Program announced last summer.

The programme initially sought to investigate liners' compliance with rules around detention and demurrage.

“American exporters deserve access to ocean transportation to sell to international markets every bit as much as overseas sellers get access to US markets,” FMC chairman Daniel Maffei said in a statement.

“The FMC’s expanded ocean carrier audit programme will provide better visibility into which ocean carriers work well with US exporters, and more importantly, which ocean carriers can and should do more to support exporters.”

Maffei said shipping companies have been cooperative so far, but would not rule out “any action within the bounds of the law” so that shipping serves both exporters and importers.

The initial audit, also known as the Ocean Carriers Audit Program, looked into the top nine liner operators: AP Moller-Maersk, Mediterranean Shipping Co, CMA CGM, COSCO Group, Hapag-Lloyd, Ocean Network Express, Evergreen, HMM and Yang Ming.

The FMC also said its Bureau of Enforcement would this week examine five more liner operators — BAL Container Line, CULines, Lihua Logistics Co, Transfar Shipping and X-Press Container Line — and the services they have been offering US exporters.

It said none of them serviced the US until port congestion caused container rates to skyrocket last year.

It said it would be looking into vessel calls made to the US since June 2021, including the number of loaded and empty containers carried on return voyages to Asia before determining whether or not to take any action against the five.

BAL, CULines, Transfar and X-Press have been approached for comment.

Contact information for Lihua Logistics was not immediately available.

The FMC, which regulates international ocean shipping as it pertains to the US, has taken a more active role since last summer when President Joe Biden signed an executive order on competition in the economy.

The order instructed the FMC to look only at detention and demurrage, but the commission has since linked with the Department of Justice's antitrust division and sought greater regulatory powers.

It also launched investigations into Ocean Network Express and Wan Hai Lines.