The teenager who hacked several passengers on a train in Germany could be a Pakistani. national broadcaster ZDF citing officials said.
German officials had earlier said he was a refugee from Afghanistan.
Security authorities are now probing whether he posed as a refugee from Afghanistan so that his chances of securing asylum was higher.
He was registered in Germany as Riaz Khan Ahmadzai.
The 17 year old, who came as an unaccompanied minor to Germany in 2015 was living with foster parents on a farm in a village in Wurzburg district of Bavaria.
5 persons were injured after the man stabbed and hacked his co-passengers with an axe and knife late on Monday.
Two of the injured are said to be critical.
Police shot dead the assailant after he tried to flee at the Wurzburg-Heiingsfeld station.
The train was running between Treuclingen and Wurzburg, a town some 387 kms from Berlin.
ISIS had claimed responsibility for the attack. The terror group had on Tuesday released a video purportedly of Riaz Khan, but mentioned him as “Mohammed Riyad”.
Investigators searching his room had discovered a hand painted ISIS flag and a farewell letter addressed to his father.
There are also reports that a Pakistani document, giving instructions on how to secure asylum was also found among his belongings.
The fact that he often used a dialect of Pashto, mostly spoken in Pakistan than in Afghanistan, also have led investigators to doubt his nationality.
Over a million asylum seekers, mostly Syrians and Afghans were allowed into Germany last year.
Bavarian Interior Minister Joachim Hermann has called for stricter border controls following the attack.
“Any one entering the country without papers and cannot prove his identity must be detained at the border and verified,” Hermann said in an interview to a German broadcaster ‘BR Fernseher’.
Calling for an overhaul in the current procedure, Hermann said that Riaz Khan’s finger prints were also not taken.
There are fears that the attacks could trigger backlash against the refugees.
several officials have warned against stereotyping asylum seekers, especially unaccompanied minors, and have urged those who had volunteered to help the refugees to continue their support.