Two child migrants arrested in January after a 12-year-old girl was forced to perform sex acts with them are now thought to be adults at least 21 years of age.

The two men who have not been named but are reported to be Iranian citizens were officially 15 and 16-years-old at the time of their arrest four weeks ago. One of the men has now been proved to be “at least 21 years old” through dental examinations, while the second is also thought to be an adult but with no conclusive evidence having yet been brought forward, reports Bild.

The men were admitted to a children’s migrant aid centre when they arrived in Dusseldorf last year after they had managed to fool the German government over their true age. Once in the centre they were allowed into the classroom alongside other children from Dusseldorf, and they were able there to gain access to the much younger girl.

She was “compelled and forced into sexual acts” over the course of some days, said the prosecutor. Germany’s Express reports a six year old boy who discovered that the girl was being abused was threatened with having his throat cut for telling on the pair.

It was reported at the time of their arrest the abuse had been established after the girl had given testimony and she had undergone a gynaecological investigation, a doctor giving his professional opinion. The girl was moved for “protection” to another facility outside of the city.

The authority responsible for the accommodation and facility have blamed severe overcrowding for the events that allowed the men to attack the girl, with reports stating the city child protection centre is “bursting at the seams”. Chief officer for youth services John Horn said of the attack that children are normally segregated by age and sex, but are able to mingle in “common spaces”.

The two suspects had always “retreated into corners” and taken precautions to avoid being properly supervised, he said.

Reticence to be seen too much by staff at the centre may be linked just as much to their falsified ages, as to their sexual attacks. That these men were able to masquerade as children is being seen as a “serious blow” to the credibility of Germany’s Youth Office, which gave the men a “qualified inspection” and certified them to be “credibly under-age” at the time of their arrival.