Story highlights Castro was the editor in chief of the Primera Hora newspaper

Earlier this month, attackers left threats next to two other bodies

Attorney general's office calls the deaths "lamentable acts"

The editor of a Mexican newspaper was found dead, her body decapitated and with a note next to it, officials said.

Maria Elizabeth Macias Castro, 39, was the editor in chief of the newspaper, Primera Hora.

Her body was found Saturday morning, according to the attorney general's office in the northern Tamaulipas state. A message "attributed to a criminal group" was found next to her, the office said.

"The state government expresses its deepest condolences to the relatives and loved ones affected by these lamentable acts," the office said, adding that it is investigating.

Earlier this month, attackers left ominous threats mentioning two websites on signs beside mutilated bodies in northern Mexico.

A woman was hogtied and disemboweled. Attackers left her topless, dangling by her feet and hands from a bridge in the border city of Nuevo Laredo. A bloodied man next to her was hanging by his hands, his right shoulder severed so deeply the bone was visible.

Signs left near the bodies declared the pair, both apparently in their 20s, were killed for posting denouncements of drug cartel activities.