The German Federal Prosecutor's Office on Sunday has taken over the investigation in the eastern city of Chemnitz of a suspected planned bomb attack which they are labelling an act of Islamist terrorism.
"The overall picture of the investigations, especially the amount of the explosive material found, points in the direction of a person who has planned to carry out an Islamist-motivated attack," a spokeswoman for the Prosecutor's Office said.
The statement came as a nationwide manhunt was triggered by the discovery of explosives in the Chemnitz flat of 22-year-old Jaber al-Bakr.
The Syrian man, who according to investigators in the state of Saxony, arrived in Germany as a refugee is suspected of planning a bomb attack and is currently on the run.
Police special forces have searched a second flat, one of several contact addresses for the suspect, on Sunday for explosives, but found none, a spokesman said.
Police detained a man from the latter location and are now questioning him.
Three other Syrian men including the lessee of al-Bakr' flat were detained Saturday. The lessee remains in police custody while the two others were released Sunday.
Police have not confirmed German media reports that the main suspect al-Baker had been in contact with the Islamic State terrorist group via internet and may have been in discussions with them over a possible target.
Security sources told dpa Saturday that there was a suspected connection to Islamic State.
Police have also refused to comment on a report by Focus magazine that a German airport was the intended target of an attack. Security was beefed up at both Tegel and Schoenefeld airports in Berlin late Saturday.
Some 890,000 migrants arrived in the country in 2015, many of whom had fled the ongoing conflict in Syria.
Germany has been on high alert since two terrorist attacks occurred over the course of one week in July. Both were claimed by Islamic State militants and carried out by asylum seekers.
At least five Islamist attacks have been thwarted by German police since 2007.