The US Federal Maritime Commission is continuing its investigations into container shipping, this time asking eight liners to provide it with documentation on recently implemented congestion surcharges.

The federal agency tasked with regulating shipping said on Wednesday that it reached out to CMA CGM, Hapag-Lloyd, HMM, Matson, Mediterranean Shipping Co, Orient Overseas Container Line (OOCL), SM Line and Zim to prove the fees were levied legally.