Firefighters have been tackling the blaze at Skip-It containers in North Quay Road, Newhaven, since Friday.
East Sussex Fire and Rescue Service said they believed the burning rubbish had been extinguished but were checking for signs of smouldering.
Crews will remain at the depot for another 24 hours.
Most of the smoke from the blaze, which had been billowing hundreds of feet into the air, cleared on Monday.
An investigation is under way into the cause of the fire.
In a statement, East Sussex Fire and Rescue Service, said: "It is believed the fire is now out but crews are working with the site operators to make sure this is the case.
"Piles of waste are being moved and checked for any signs of smouldering.
"It is likely that we will remain on site for a further 24 hours, along with other agencies including the Environment Agency."
Skip-It said the waste was compacted, baled household waste due to be exported to Germany for burning in an incinerator.
Fire crews believe they have finally extinguished 200 tonnes of rubbish that was alight for six days, sending smoke hundreds of feet into the air.