The planned nationwide test alarm revealed the gaps and gaps in Germany's warning system.
The Federal Ministry of the Interior classified the test alarm as a failure on the first nationwide warning day.
"The triggering of the test alarm on today's warning day 2020 failed due to a technical problem," said a message from the ministry.
For the first nationwide warning day, sirens were supposed to wail all over the country at eleven o'clock, the warning apps NINA and KATWARN were to be activated, and information was to be distributed via radio and television.
The all-clear should be given 20 minutes later.
In fact, the Federal Office for Civil Protection and Disaster Aid (BBK) only initiated the official hazard report half an hour later than planned.
The trial all-clear followed around ten minutes later.
The reason for the delay in the planned nationwide report was the "unexpected simultaneous triggering of a large number of warning reports," it said.
It was therefore intended that only the BKK responsible for the federal level would trigger warning messages.
But the states and municipalities also sent their own requests.
They then blocked each other so that the system failed.
If necessary, appropriate technical precautions would have to be taken so that such a breakdown does not happen again, said BKK President Christoph Unger.
In some places, the population initially did not notice anything from the test alarm.
In Munich, for example, a fire department spokesman said there had been no sirens in the state capital for many years.
They were gradually dismantled after the end of the Cold War.
The same applies to large parts of Berlin.
The so-called warning day, which is to take place every year on the second Thursday in September, serves as preparation for dangerous situations such as floods, chemical accidents or terrorist attacks.
In addition to sirens, media and warning apps, digital billboards and loudspeaker trucks should also be integrated.
The interior ministry announced that the breakdown will now be "fully processed" and the findings will be taken into account in the further development of the warning system.
According to a decision by the Conference of Interior Ministers, the nationwide warning day will take place annually on the second Thursday in September from 2020.