A wildfire on the front line of the Ukraine war zone made several landmines explode At least six have blown up on the frontline.

BELGRADE, Serbia -- Wildfires caused by the hot summer sun heating up overgrown abandoned cropland triggered at least six landmines to explode on the front line of a war zone in eastern Ukraine.

Emergency officials told ABC News that 21 firefighters and five engines were working on Thursday to contain the blaze, which covered two-and-a-half acres of a minefield on the front line of a government-controlled area. No injuries have been reported so far.

The blaze and landmine explosions required a major crossing point between government- and rebel-held areas, known as the Novotroitsk crossing, to remain closed for a second day, authorities said. Around 40,000 civilians cross the front lines daily, according to the Organization for Security and Co-operation in Europe, and the Novotroitsk crossing is one of only five.

The OSCE, which had a team on the ground Wednesday and heard the landmines exploding, facilitated a local ceasefire, an OSCE official said.

“We established a dialogue between the sides, so firefighters can continue to battle the fire,” Alexander Hug, OSCE principal deputy chief monitor, told ABC News.

It's unclear how many landmines are planted across eastern Ukraine, but the region, known as the Donbass, is one of most mined areas in the world.

"Nobody knows how big the mine problem is,” Hug explained. “We just know it’s big.”

Both sides of the conflict have laid landmines and unexploded ordnance, denying people the opportunity to use the land for crops and livestock.

Landmines are so prevalent in the Donbass that eastern Ukrainians on both sides have nicknamed them “potatoes.”

Since the beginning of the conflict in 2014, the use of landmines on both sides has resulted in 1,796 casualties, including 238 civilian deaths and 491 injuries, Halo Trust, a British nonprofit organization that removes landmines, told ABC News.