MEXICO CITY — Mexican gangs control 60 percent of the country's prisons, where they hold cell keys, punish inmates and charge for protection, a human rights report said in the wake of a mass escape.

The government's National Human Rights Commission issued the report after visiting around 100 state prisons across Mexico where investigators found poor security conditions.

"Sixty percent of them were self-governed," said the nation's ombudsman, Raul Plascencia, adding that inmates sell all sorts of goods including food and mobile phones.

"The deterioration of prisons in the last few years is undeniable, as demonstrated by the escapes, fights, self-governing and assaults on prison personnel," he said.

The report was issued one week after 131 inmates escaped from prison in Piedras Negras, a city on the US border. Sixteen prison guards, including the director, have been detained over their possible role in the escape.

In the last two years, 521 inmates have run free in 14 prison escapes while 352 homicides have been committed inside penitentiaries, the ombudsman said.

Illegal substances are found in prisons, including weapons and drugs. Prostitutes are allowed inside, and groups often attack others or control the rest of the prison population, he said.

Mexico has 419 prisons, including 13 controlled by the federal government while the rest are managed by state and municipal authorities.