BERLIN, Germany -- Werder Bremen have admitted flying a drone over Hoffenheim's training ground ahead of Wednesday's 1-1 draw between the two clubs.
Earlier this week, Hoffenheim reported an "unannounced drone flight" to police and told ESPN FC they had done so because of "security concerns."
"Werder Bremen this past Tuesday briefly used a drone," a statement on Bremen's website said. "This is a result of talks between Bremen executive Frank Baumann, head coach Florian Kohfeldt and the employees of the analysis department."
Earlier this week in London, a drone flying over the airfield at Gatwick Airport caused major disruptions in air travel in Europe.
Baumann was quoted as saying: "We've discussed this internally, and I accept responsibility for it.
"If those events at Hoffenheim led to a certain insecurity on the training pitch, I would like to apologise for it."
Speaking at his postmatch news conference following the draw, Hoffenheim coach Julian Nagelsmann said he did not mind Bremen spying on training but had been concerned about the safety of his players.
"If you fly such a things over people and there's a technical defect, it might have serious consequences," Nagelsmann said.
On Thursday, Mannheim police told ESPN FC they were hoping to identify the person or people operating the drone.
Police said they would then determine whether its use was permitted under the German Drone Act which stipulates that, depending on the weight of the drone, permission must be obtained from local authorities.
The legislation also prohibits the use of drones weighing more than 0.25 kilograms over a crowd of people or over inhabited areas. Under the country's Air Traffic Act, regulatory offences can be punishable by a fine of up to €50,000.
Early last year, Hoffenheim tested the use of a drone in training but the idea was soon abandoned.
Chief executive Dr. Peter Goerlich told ESPN FC at the time that the drone had turned out to be "rather disturbing and distracting" for the players.