All restrictions on marine traffic through the Houston Ship Channel, a critical waterway for oil shipments, were lifted on Thursday, five days after an oil spill in the Galveston Bay, the U.S. Coast Guard said.

The channel was shut on Saturday when a Kirby Inland Marine fuel oil barge collided with a cargo ship near the entrance to Galveston Bay, spilling 4,000 barrels, or 168,000 gallons (636,000 liters), of heavy, black fuel oil.

The waterway reopened on Tuesday, though ships had to check in at inspection and decontamination stations along the channel.

The Coast Guard had banned ships from moving along the channel at night to prevent vessels from spreading the oil to the northern end of the Bay.

The unusually lengthy closure of the waterway, which connects the Gulf of Mexico to inland terminals and facilities, halted imports of crude to refiners that account for more than one-tenth of U.S. refining capacity and delayed exports of some products. More than 100 large vessels, many of them oil tankers, were forced to queue up on either side of the channel.