The engineer, who was not identified, was abducted from a road-building project on a bridge on the outskirts of Kano, CNN reported.
Police said they had not determined whether the militant Islamist group Boko Haram or criminal gang members were responsible.
The German foreign ministry is investigating, a spokeswoman said.
Officials with Dantata & Sawoe, the company for which the engineer works, could not be reached for comment, CNN said.
Boko Haram, whose name means "Western education is forbidden," is not known to have been involved in kidnappings of foreign workers, the U.S. network said.
Abductions by criminal gangs are common in Nigeria where the U.S. embassy in Abuja confirmed a U.S. citizen had been kidnapped last Friday in Nigeria's Delta state.
More than 200 people were killed in violence in Kano last Friday, community leaders say. Security sources told CNN this week a joint military task force in Kano had arrested 158 members of Boko Haram.
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