Authorities in Mexico have seized two homemade armored freight trucks believed to be altered for local drug cartels during a raid and shootout in a warehouse in the northern state of Tamaulipas.

Two suspected drug traffickers were killed during the raid in the town of Camargo. Authorities say the tanks – dubbed “monster trucks” by security forces – were fitted with 2.5-centimeter thick armor and primitive gun turrets.

At least 23 other trucks were also found at the warehouse, some already partly modified. Mexican authorities say monster trucks are powerful – the welded Armour can resist fire from heavy caliber machine guns and can only be destroyed by anti-tank weapons.