Christoph Metzelder is under preliminary investigation over allegations of distributing child pornography, authorities in Hamburg have confirmed.

Former Germany international Metzelder is accused of using WhatsApp to send images featuring child pornographic content.

"As part of the preliminary investigation on Tuesday, September 3, two search warrants of the district court of Hamburg in Dusseldorf were enforced," said the Hamburg attorney general's office in a statement. 

"As part of the search, data carriers were taken as evidence for review.

"The search was carried out by officials of the Hamburg State Criminal Police.

"The accused acted cooperatively during the police action.

"The evidence will now be evaluated. The investigation continues."

Metzelder, who won 47 caps for Germany between 2001 and 2008, played for clubs including Borussia Dortmund, Real Madrid and Schalke.