An arson¹ attack in the northern Mexican city of Monterrey has left at least 53 people dead.

墨西哥北部城市蒙特雷一座赌场被纵火，至少53人死亡。

Gunmen burst into the building in broad daylight（在大白天） , dousing²（平息，浸透） it with fuel and setting it alight.

Fire crews had to free dozens of people trapped by smoke and flames.

Officials suspect organised crime was behind the attack, one of the deadliest since President Felipe Calderon launched his crackdown on the cartels in December 2006.

In a tweet, Mr Calderon said the attack was "an abhorrent³（可恶的） act of terror and barbarism（野蛮，原始） " that requires "all of us to persevere⁴ in the fight against these unscrupulous（肆无忌惮的） criminal bands."

State police officials quoted survivors⁵ as saying gunmen had burst into the premises⁶ and tried to rob it, before emptying fuel from tanks they had brought with them, AP news agency reported.

Officials said those inside had hidden in toilets and offices when they heard explosions instead of trying to get out and had suffocated⁷（窒息） as smoke engulfed⁸ the building.

Some reports suggest the emergency doors of the premises had been locked.

TV images showed relatives outside the casino demanding information about their loved ones.

"My wife came here for a celebration... she was having dinner with her friends," one man told Milenio TV as wept, Reuters reported.

State Attorney General Leon Adrian de la Garza said a drug cartel was believed to be responsible for the attack and warned that more bodies may be found.

Home to some of Mexico's largest companies, Monterrey and the state of Nuevo Leon have seen rising violence as the Zetas and Gulf⁹ cartels vie for for control of trafficking routes to the US.