Up to 200 tonnes of waste caught fire at the Mick George waste site in Rushton last night (Tuesday).
Crews from Northamptonshire Fire and Rescue Service (NFRS) raced to the Oakley Road depot just before 10.30pm with five appliances, an aerial ladder platform and two water bowsers in attendance.
A thick plume of smoke surrounded the nearby area with two pumps still at the scene this morning.
Another huge fire also started in Northampton just before midnight.
A fire and rescue spokesman said: "Smoke plumes at both incidents have decreased substantially since last update.
"Current advice for nearby residents is to keep doors and windows closed only if your property is affected by residual smoke."
Fire crews are expected to remain at the Mick George site for between 24 and 48 hours due to the deep seated nature of the fire, which involves the recycling unit and about 200 tonnes of household waste.
A Mick George spokesman said the fire was likely to be as a result of the current heatwave.
The spokesman said: “Mick George Ltd can confirm a fire was reported at its Rushton transfer station on Tuesday, July 23, at about 10pm.
"The cause of the fire has not yet been identified, however it is most likely a consequence of the current record-breaking heatwave being experienced across the country.
“All Mick George Ltd recycling facilities have fire plans in place and are monitored 24/7 with permanent staff.
"The management team at Rushton transfer station acted quickly on discovering the fire and contacted Northamptonshire Fire and Rescue Service (NFRS) who were very quickly on the scene and brought the fire under control. NFRS are continuing to monitor the situation with the support of Mick George Ltd staff."
The Environment Agency and public health services have been made aware of the fire. A national waste fire tactical advisor is currently at the scene.
There are not believed to be any casualties and the cause will be investigated.
Refuse collected by East Northamptonshire Council normally gets tipped at the site and there may be disruptions to collections as a result.
A council spokesman said: "Following a fire at our tipping point for refuse last night, there may be some disruption to our refuse collection rounds this week. Some collections will take place considerably later than normal due to the extra distance to tip.
"Please leave your refuse bin out if it is not collected at your usual time. Recycling collections are not affected as these are tipped off elsewhere for bulking up before onward transport to the sorting facility."
An Environment Agency spokesman said: “Our officers are working with Northamptonshire Fire and Rescue to check on potential pollution from fire water run off.
"This has been contained and no off site water pollution is expected.
"Our officers will continue to monitor the situation. If people have concerns about this incident they should call our 24-hour hotline on 0800 807060.”