By Victor Hugo Valdivia
MONTERREY, Mexico (Reuters) - Armed men threw a grenade into a casino in northern Mexico, killing at least two people and setting fire to the building, local media and a Reuters witness reported on Thursday.
A dozen people are presumed to be trapped inside the Casino Royale building as smoke poured out into the street.
"There is a plume of dark, thick smoke towering from the building," a Reuters witness at the scene said. The army, Red Cross and firemen were at the scene while nurses started to line up stretchers.
Local media said there were at least two people killed in the attack, but some are putting the toll as high as 10.
Monterrey, a manufacturing city of 4 million people 140 miles from the Texan border, has become increasingly violent in the last year as the government's war against drug cartels has enveloped the city, although it was not clear whether organized crime was involved in the grenade attack.
This is the second incident involving grenades in Mexico this month. Two weeks ago, another group of armed men hurled a grenade into a popular area of the Gulf port city of Veracruz, killing one person.
(Additional reporting by Cyntia Barrera Diaz; editing by Anthony Boadle)