Police have detained one person in connection with false email bomb threats that led to the evacuation of hundreds of people from more than 20 hospitals, courts, police stations and prosecutors' offices across Poland, the interior minister said.
Bartlomiej Sienkiewicz said Poland's investigators were in touch with counterparts in the United States, France and Germany, because some of the emails were sent from servers in those countries. He refused to give any details about the detained person.
Police who checked all the locations said that no explosives were found and there were no explosions at noon as the emails had threatened. One hospital in southern Poland was fully evacuated, one in Warsaw partially.
"The entire day was lost for us and for the patients," said Wlodzimierz Migacz, director of a hospital in Katowice, who ordered a full evacuation, including of a premature baby in an incubator.
"I hope the author of the email will be found and punished," Mr Migacz said on TVN24.
TVN24 footage showed ambulances leaving the hospital to take patients to other medical centres. In Warsaw, it showed some patients and relatives waiting in front of a hospital.
People were allowed to return to the buildings on Tuesday afternoon.
Mr Sienkiewicz said there was no danger to anybody's life or health and that the threats were a case of "unbelievable cheek" on an unprecedented scale.
A false bomb threat leading to major disruption carries a maximum prison sentence of eight years.