Evacuees spent Christmas in the centres - schools converted into temporary shelters - and will likely spend up to four months there should the volcano continue rumbling, according to provincial authorities.
"I have already declared my province open season for all aid agencies," Governor Joey Salceda told IRIN.
"They don't have to go to my office any more to secure permission. We need all the help we can get at this hour of need."
Standby emergency funds from the local government may only last for four weeks, and resources were fast dwindling, he warned.
"Our hope is that Mayon will not continue with this phase since the schools have to re-open after the Christmas break," he said.
But the deep rumblings, ash fall and lava flows are indicative of a dangerous and imminent eruption.
To date, close to 10,000 families or 47,285 people from hundreds of villages in five townships inside an extended 8km danger zone have been evacuated since volcanic activity started on 14 December.
Since the evacuation, however, many of the men were reportedly sneaking out of the camps in the daytime to check on their farms in the foothills of Mayon.
While they are "actively being discouraged" from doing so, Governor Salceda said it was almost impossible to monitor each and every person in the camps.
No room for complacency
Meanwhile, experts have reiterated the need not to be complacent: Renato Solidum, head of the Philippine Institute of Volcanology and Seismology, said "a hazardous eruption remains likely within days."
The institute's observatory in Legaspi city near Mayon reported at least nine ash explosions accompanied by rumblings in the 24 hours up till 7am on 28 December.
The explosions sent ash and lava fragments up to 2,000m into the air, covering villages and towns with a thin layer of fine particles that scientists warn could also cause respiratory and skin problems.
Some 44 volcanic quakes were also recorded by seismic machines, it said.
Tons of relief supplies have been trucked into the evacuation centres, and temporary tent clinics and hospitals have also been set up. Water and sanitation facilities, however, were in critically short supply.
The UN Children's Fund (UNICEF) said it had provided over US$100,000 in supplies to address the urgent needs of children and their families, including water kits and medical supplies such as face masks.
"Our hearts go out to the thousands of children and families who have been affected by the eruption," UNICEF country representative Vanessa Tobin said, but expressed relief that there had so far been no reports of any casualties.
UNICEF said it was concerned for the more than 24,000 children whose schools have been converted into temporary shelters, and promised to bring in school tents and tuition packs to ensure classes can resume after the Christmas break.
Meanwhile, Eric Tayag, head of the National Epidemiology Centre, has advised those in evacuation centres to protect their children from Mayon's fine ash, warning that it could exacerbate asthma, bronchitis and respiratory-related illnesses.
"While illnesses caused by ash fall may not be that dangerous, people should take precautions and stay indoors if they can. For those in evacuation centres, prepare a wet cloth to cover the nose and mouth in cases of heavy ash fall. Those with asthma, bronchitis and emphysema should take precautions," he said.
"They may experience increased attacks because ash fall, when inhaled, can trigger breathing problems."
The 2,460m high Mayon is the most active of the Philippines 22 active volcanoes. It has erupted 48 times in recorded history, and in 1814 buried the entire town of Cagsawa, killing over 1,200 people.
Three months after it last erupted - in August 2006 - a typhoon dislodged tons of volcanic debris from its slopes, triggering a mudslide that buried entire villages and leaving over 1,000 dead.