Almost 50 fire-fighters spent several hours yesterday tackling the fire, which could be seen for miles across the city skyline.
The Fire Service was alerted to the blaze shortly before 11am with plumes of thick black smoke soon spreading from the port.
Residents in the area were told to keep their doors and windows closed and to remain indoors as fire crews dealt with the unfolding situation.?
Police had also appealed for people to avoid the area around Port Road, Strathfoyle, to allow fire crews “space to work”.
The Port Road was closed as fire crews and 12 appliances, including high-reach aerial appliances and a command support vehicle, tackled the blaze.
The spokesperson said the Northern Ireland Fire and Rescue Service (NIFRS) was “working closely with the Harbour Master to deal with the situation”.
Speaking as crews continued their work yesterday, NIFRS group commander William Johnson said 46 firefighters were involved in the operation.
“Crews are currently involved in firefighting activity to contain a fire within a large grain shed and are working closely with the Harbour Master to deal with the situation,” he said.
“We would ask everyone to avoid the area to allow our crews to combat the fire and local residents are advised to keep their doors and windows closed.”
A spokesperson for Foyle Port said the fire was in a sheds on its site. There were no reports of any injuries.
Sinn Féin councillor Paul Fleming said: “There was concern in the local community here at the scale of this fire and if it could spread.
“Thankfully the wind direction kept the large plumes of smoke away from local homes along with the efforts of the Fire Service.
“I would like to pay tribute to the Fire Service for the work they carried here in preventing it from spreading.”