"We are assuming there is no suspect in the building," a Berlin police spokesman told German news agency DPA on Tuesday afternoon.
Police will continue to investigate and plan to question teachers and students at Trade College No. 1, he said. A caller reported a man with a gun at about 9 a.m. on Tuesday at the technical college, a sprawling campus on Wrangelstrasse in the Berlin district of Kreuzberg.
Police remain unsure whether the call was a false alarm, according to DPA.
Teachers and students were evacuated and the streets surrounding the school closed as a helicopter circled overhead and a police team with dogs searched for the reported gunman. More than 100 officers were called to the school.
"We don't know if the armed person is still in the school or ever was in the school," Gabi Kobbe, a police spokeswoman, told The Local at midday, as the search was still going on.
The trade college is not known as a problem school, Kobbe said.
The school houses more than 6,000 students and 260 teachers across a sprawling complex of post- and pre-war buildings, including former Prussian barracks. On its web site, the school calls itself the largest trade college in Germany.