Sch 2 para 17
(1) A person liable to be detained under paragraph 16 above may be arrested without warrant by a constable or by an immigration officer. (2) If— (a) a justice of the peace is by written information on oath satisfied that there is reasonable ground for suspecting that a person liable to be arrested under this paragraph is to be found on any premises; or (b) in Scotland, a sheriff, or a . . . justice of the peace, having jurisdiction in the place where the premises are situated is by evidence on oath so satisfied; he may grant a warrant authorising any immigration officer or constable to enter , if need be by reasonable force , the premises named in the warrant for the purpose of searching for and arresting that person. (3) Sub-paragraph (4) applies where an immigration officer or constable— (a) enters premises in reliance on a warrant under sub-paragraph (2), and (b) detains a person on the premises. (4) A detainee custody officer may enter the premises, if need be by reasonable force, for the purpose of carrying out a search. (5) In sub-paragraph (4)— “ detainee custody officer ” means a person in respect of whom a certificate of authorisation is in force under section 154 of the Immigration and Asylum Act 1999 (c. 33) (detained persons: escort and custody), and “ search ” means a search under paragraph 2(1)(a) of Schedule 13 to that Act (escort arrangements: power to search detained person).