Former German intelligence chief August Hanning, who was arrested on Tuesday on suspicion of espionage and attempted treason, is being investigated over alleged links to Azerbaijani intelligence, according to Der Spiegel.

Hanning, 80, headed Germany’s Federal Intelligence Service, the BND, from 1998 to 2005. German federal prosecutors say he is suspected of obtaining classified information and using material derived from it in contacts with a foreign intelligence official.

According to Der Spiegel, investigators believe the foreign intelligence officer involved was Azerbaijani. Hanning allegedly obtained classified BND documents from his former associate Manfred D. and used the information to prepare a written intelligence analysis intended for the Azerbaijani officer. Whether the analysis ultimately reached its intended recipient remains under investigation.

Hanning is also known to have maintained connections with Azerbaijan. He previously served on the board of the German-Azerbaijani Forum, an organization promoting relations between the two countries.

German authorities arrested both Hanning and Manfred D. on October 6. Prosecutors are investigating Hanning on suspicion of treasonous espionage, obtaining state secrets, attempted treason and acting as an agent for a foreign intelligence service.

German prosecutors have not officially identified Azerbaijan as the foreign state involved. The reported Azerbaijani connection is based on information attributed to investigators by Der Spiegel.

Hanning’s lawyer has declined to comment publicly on the allegations concerning Azerbaijan.