(1) If, in England and Wales or Northern Ireland, on an application made by a constable a justice of the peace is satisfied that there are reasonable grounds for believing-

(a) that a dangerous substance is kept or used in any premises but that no notice under section 59 is in force in respect of the premises, or

(b) that the occupier of any relevant premises is failing to comply with any direction given to him under section 62 or 63,

and that any of the conditions mentioned in subsection (4) apply, he may issue a warrant authorising a constable to enter the premises, if necessary by force, and to search them.

(2) If, in Scotland, on an application made by the procurator fiscal the sheriff is satisfied as mentioned in subsection (1), he may issue a warrant authorising a constable to enter the premises, if necessary by force, and to search them.

(3) A constable may seize and retain anything which he believes is or contains a dangerous substance.

(4) The conditions mentioned in subsection (1) are-

(a) that it is not practicable to communicate with any person entitled to grant entry to the premises;