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The Houston Pilots Association believes that a March 2015 collision between two tankers that caused a chemical spillage in the Houston Ship Channel and closed the 50 mile channel for four days, was the result of a fuel switch, Houston Chronicle reports.

Houston officials have been urged by the National Transportation Safety Board (NTSB) to employ better bridge management and communications in the Channel, which is the home of one of the largest petrochemical complexes in the world.

In their report, they cited heavy fog as being a contributing factor to the Conti Peridot striking a chemical tanker, the Carla Maersk, as well as the pilot failing both to communicate and to control the vessel.

The report specifically asks the Lone Star Safety Committee - a group of industry representatives, government officials and pilots based in Houston - to address how they can improve safety in hazardous weather. The NTSB recommended an array of measures, such as anchoring, one-way traffic and increased vessel separation.

Association officials are challenging a federal review blaming pilot error for the incident. They argue that the blame lay in changing to ultra-low-sulphur fuel oil. The officials contend that the that the Conti Peridot unexpectedly lost power due to the fuel change, just seconds before the crash during which around 88,000 gallons of flammable chemicals were spilled and no one was injured.