s 28C Search and arrest without warrant.
(1) An immigration officer may enter and search any premises for the purpose of arresting a person for an offence under section 25 or 25A . (2) The power may be exercised— (a) only to the extent that it is reasonably required for that purpose; and (b) only if the officer has reasonable grounds for believing that the person whom he is seeking is on the premises. (3) In relation to premises consisting of two or more separate dwellings, the power is limited to entering and searching— (a) any parts of the premises which the occupiers of any dwelling comprised in the premises use in common with the occupiers of any such other dwelling; and (b) any such dwelling in which the officer has reasonable grounds for believing that the person whom he is seeking may be. (4) The power may be exercised only if the officer produces identification showing that he is an immigration officer (whether or not he is asked to do so).