Abergavenny fire services responded after a bale of hay was deliberately set on fire near the Eisteddfod site on Llanfoist Bridge last night.
South Wales Fire and Rescue Service says the fire in the Sirhowy Valley has devastated 300 hectares of forest and grassland.
Scores of firefighters have been tackling the blaze at Wattsville which will be left to burn until later this morning when the area can be assessed from the air.
At one stage it threatened nearby homes.
It is thought to have been started deliberately. People can call 101 if they saw saw something suspicious.
Two people have been treated for smoke inhalation after a fire at a house at Morlan Terrace in Burry Port.
Firefighters were called out just after 0130 to the two storey terraced property. The pair were rescued from a flat roof.
An investigation will continue this morning.
A person has been taken to hospital after a flat fire in the Penybryn area of Gelligaer.
Crews from Aberbargoed and Treharris were called to the blaze shortly after 10pm last night. The flat was severely damaged.
Firefighters say they are tackling 2000 tonnes of building waste.
But the operation is being hampered because of 30 to 40 gas cylinders, nearby, of 'varying content'
They say these have to be kept cool to 'avoid the risk of explosion and danger to firefighters'.
More equipment's being drafted in to tackle a large fire at a recycling centre on the outskirts of Cardiff.
The alert was sounded at around 1:30 this morning. Around 60 firefighters are at the scene.
The fire involves several industrial units, vehicles, and large quantities of refuse. A high volume pump has been called to use water from nearby reens and ponds.
South Wales Police:
'At 0155 hours on Friday 28th March 2014 Police and South Wales Fire and Rescue Service attended a report of a fire at the Atlantic Waste Management site, Rumney, Cardiff.'
'The fire currently extends over a five acre site and a two hundred metre exclusion zone has been implemented due to the presence of gas canisters within the site. Newton Road is currently closed. The cause of the fire has not yet been established.'
Around 60 firefighters are tackling a blaze at a recycling centre on the outskirts of Cardiff.
They were called out at around 1:30 this morning to a recycling firm on Newton Road, Rumney. The fire involves several industrial units and large quantities of refuse.
It's being described as a "protracted incident"