According to South Wales Fire & Rescue Service, crews were called to the site at Vale Business Park in Llandow at 5.13am yesterday.
Vale of Glamorgan council, which is handling enquiries for the incident, said recyclable materials such as paper and plastic have caught fire at the site, although no hazardous waste has been affected.
It is anticipated that the fire could last for a number of days, following a multi-agency meeting to assess the situation yesterday, which involved South Wales Fire & Rescue Service, South Wales Police, Public Health Wales, Natural Resources Wales, Welsh Water and the Vale of Glamorgan Council.
Another fire hit Siteservs waste transfer station on the same premises earlier this month (see letsrecycle.com story), although the council confirmed that the yesterdays blaze took place at a different location on the site.
A spokeswoman for Siteserv said that it was unsure of the source of the fire, but that firefighters were quick to respond and were still working to bring flames under control yesterday afternoon.
Earlier on Tuesday, plumes of smoke could be seen from as far away as Cardiff city centre.
The Siteserv spokeswoman said: Whilst we are unsure of the source of the fire, we are working with both the fire service and police to establish possible causes. In the meantime, the management team has implemented its Disaster Recovery Plan. We are otherwise operating business as usual.
It has been confirmed that there is no asbestos within the MRF building but local residents were warned to keep windows and doors closed as a precaution.
According to the fire service, at one stage 86 personnel were committed to the incident, with eight water ladders, six water bowsers, two hydraulic platforms, a high volume pump, an environment appliance, a welfare unit and a control unit.
A spokesperson for the council said: The plume of smoke is rising and dispersing and current evidence suggests that the smoke is not at ground level. Small fragments of ash may fall out of the plume, but the risk to health is very low. We do not expect people living in the immediate vicinity to be exposed, but if smoke is noticed at ground level you are advised to stay indoors and close doors and windows.
The council also said that some local residents may have experienced reduced water pressure, as local water resources were being used to tackle the blaze.
Siteserv Recycling was set up around 15 years ago and processes 133,000 tonnes of business waste material each year, including paper, plastics, wood, metal and hazardous waste. The firm also claims to process 18,000 tonnes of waste from local authorities.
Siteserv customers and suppliers with questions are advised to call the companys office.