(CNN) The alleged rape of a young woman suspected to have been carried out by boys as young as 12 has sparked a debate in Germany around lowering the age of criminal responsibility of young offenders.

Three 14-year-old boys and two 12-year-old boys are being investigated after locals found a woman surrounded by two males in Mülheim, near Cologne, Essen Police said in a statement. All five suspects are Bulgarian, police added.

A police spokesman told CNN that one 14-year-old had appeared before an investigating judge, and is known to police for two previous sex offenses.

As children under 14 cannot be prosecuted under German judicial law, the teenager was too young to be brought to justice, the spokesman added.

Essen Police described the alleged incident as a "serious" sex offense, which took place at around 10:15 p.m. local time on Friday. Local dogwalkers first noticed the nervousness of their pets and they eventually found the young woman with two men in a park behind their garden.

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