No one was injured, but the explosion caused extensive property damage.
Investigators say a military convoy was chasing a suspicious vehicle and a small car exploded as the convoy passed.
Police in Monterrey are trying to determine if the car was packed with explosives or if someone threw grenades at the car.
Monterrey has seen more drug violence since early last year when the Gulf drug cartel and paramilitary drug gang the /*Zetas*/ began a fierce fight to control the area.
