Not two hours after Mark Masschelein checked on the 2,100 pigs in his barn Tuesday, an early-morning passerby was pounding on his door, pointing to the wall of flame at the back of the farm.

The result was another six-­figure loss and more heartache from another massive fire, the fourth in only two weeks in Southwestern Ontario’s farm belt.

Since Jan. 4 — when fire ripped through a Guelph-area barn at Canada’s premier harness-racing training centre killing 43 horses — nearly 3,000 animals have died and millions in losses have piled up. The fires — still under investigation — have left farm safety experts shaking their heads at so much destruction in so short a time.

That fires are preventable, but at a cost, only adds to the fallout, some say.

Barns are especially vulnerable to fire because many are old, built of wood and filled with hay and straw.

When temperatures plunge, as they have since the rash of fires began early this month, risks also rise from overloaded electrical systems, equipment used to thaw frozen pipes and rodents chewing through wires.

Once a fire breaks out in a barn, it can quickly race through it. Early estimates put losses in the millions.

“The material is very combustible and when you open the doors it creates a wind tunnel that makes the fire and smoke very intense,” said Dean Anderson, past chairperson of the Canadian Agricultural Safety Association.

Alarms and monitoring systems are available but have to be durable and affordable for the farmer, who has to weigh their cost, said Don McCabe, president of the Ontario Federation of Agriculture.

“The value of what you have is going to determine what level of security you are going to apply,” he said, noting the pile-up of recent fires in Southwestern Ontario stands out.

“Farmers care about animal welfare,” he said. “It’s extremely unfortunate that we have had so many barn fires. Winter has really just started in the last few weeks.”

The pigs destroyed in Tuesday’s blaze were just weeks from being taken to market, worth about $350,000, and the barn another $900,000, said Joris Masschelein, Mark Masschelein’s uncle and owner of the pigs.

Joris Masschelein has been farming for three decades. His nephew, who custom-feeds the pigs, has been in the business for the past 15 years and has young children. The fire will change everyone’s lives, he said.

“He checked on the barn at 1 a.m., turned on the feed mill, everything was fine,” Joris Masschelein said. “Someone came pounding on the door at 2:30 a.m. because they noticed the fire. By 3 a.m. it was completely engulfed.”

“It’s devastating for the families,” said Murray Hathaway, Middlesex County’s fire investigator, while waiting for the Ontario Fire Marshall to arrive at the pig barn fire on Parkhill Drive.

Hathaway was also at a $2-million barn fire near Delaware on Sunday that killed 500 milking goats and 30 head of cattle and destroyed the barn.

Fires can be spread quickly by high winds which whip through barns once curtains, which allow airflow in barns, ignite. The wind is then free to move through the structure, spreading rapidly.

McCabe said the fallout continues long after the flames are put out. Farmers lose livestock, their cash flow is cut off and they face the daunting task of rebuilding their herds,

Ten days after the Jan. 4 fire at Classy Lane Stables, the standardbred horse-training centre built by former Dorchester contractor Jamie Millier and his wife, Barb, 13 horses died in a fire near Mount Forest.

Trainers returning their animals to the barn first detected the blaze at Classy Lane. Some tried to rescue the horses, but were turned back by the smoke and flames.

Some owners whose animals were lost likened the blow to deaths in a family.

Anderson said getting livestock out of a burning barn isn’t just a matter of opening the doors and letting the animals run out. He recalls a fire at his grandfather’s cattle barn, caused by a heat lamp thawing a water line.

“As fast as my cousins took the cattle out, they ran back in the barn because they felt secure there. They all died huddled in one corner of the barn,” he said.

Sprinkler systems aren’t required by law in animal barns and can be prohibitively expensive.

Dan Reymer, president of the Canadian Farm Builders Association, said an update to the national farm building code, unchanged since 1995, is underway. He said fire safety has improved as wooden walls have been replaced with so-called “sandwich” walls — two layers of concrete with styrofoam in the middle.

Many livestock farmers typically now have a system that warns them by phone if their barn temperature suddenly rises or falls, said Reymer, but sprinkler systems in barns are rare because of their cost.

Raising the risk, remote farm locations can mean delays getting firefighters there and the water supply to fight the blaze may be limited.

Modern barns can be more resistant to fire because of their better wiring, remote sensors and cameras, fire walls and explosion-proof switches and water pipes and low-wattage heaters to keep pipes from freezing, said Reymer, a partner at Middlesex Concrete Forming Ltd. in Kerwood.

Two weeks of carnage