Twelve Turkish soldiers died from methane gas poisoning while searching a cave in northern Iraq for the remains of a comrade killed by Kurdish fighters three years ago, the Turkish Defense Ministry confirmed on Monday.

Initially, the ministry reported eight fatalities but later updated the death toll to twelve after four more soldiers succumbed to the gas exposure.

In a statement on X (formerly Twitter), the ministry said, "Four others of our heroic comrades in arms, affected by methane gas, have died... bringing the total number of victims to 12." Methane, a colorless, odorless, and flammable gas, can cause asphyxiation in high concentrations.

The tragedy occurred during a mission in a cave believed to have been used as a field hospital by the Kurdistan Workers' Party (PKK), a militant group Turkey has been fighting for decades.

"During a search operation in a cave... previously known to have been used as a hospital, 19 of our personnel were exposed to methane gas," the ministry said on Sunday. Other affected soldiers were hospitalized for treatment.

The operation took place in the "Claw-Lock Operation" zone, a military campaign Turkey launched in April 2022 against PKK militants hiding in border caves. The soldiers were searching for the remains of a fellow soldier killed by "terrorist gunfire." Recovery teams have been scouring the area for the past three years.

Turkey and the PKK have been engaged in a 40-year conflict, with clashes often spilling into Iraq and Syria. The violence has claimed an estimated 40,000 lives.

The cave where the poisoning occurred is situated 852 meters (2,795 feet) above sea level and had previously served as a PKK field hospital.

Despite the tragedy, Turkey remains in talks with the PKK to end hostilities after the group agreed to halt its armed struggle. However, tensions persist, with military operations continuing in the region.