A foreigner detained by the police pursuant according to Section 27 of Act No. 273/2008 Sb. or 326/1999 Sb. undergo a PCR test.
THE ACTUAL WORDING REMAINS THE SAME UNDER THE NEW MEASURE
According to point I/21 (only in Czech) the Ministry of the Czech Republic orders:
foreigners detained pursuant to Section 27 of Act No. 273/2008 Coll., on the Police of the Czech Republic, or pursuant to Act No. 326/1999 Coll., on the stay of foreigners in the territory of the Czech Republic and on the amendment of certain acts, as amended, to tolerate the collection of a biological sample in order to determine the presence of the COVID-19 disease and to provide medical personnel with the necessary assistance in carrying out this collection at the collection point of the health service provider or in the facility for the detention of foreigners.
The full wording of the measure can be found here (only in Czech).