(1) Whenever any person is arrested and detained in custody, and it appears that the investigation cannot be completed within the period of twenty-four hours fixed by section 57, and there are grounds for believing that the accusation or information is well-founded, the officer in charge of the police station or the police officer making the investigation, if he is not below the rank of sub-inspector, shall forthwith transmit to the nearest Judicial Magistrate a copy of the entries in the diary hereinafter prescribed relating to the case, and shall at the same time forward the accused to such Magistrate.
(2) The Magistrate to whom an accused person is forwarded under this section may, whether he has or has not jurisdiction to try the case, from time to time, authorise the detention of the accused in such custody as such Magistrate thinks fit, for a term not exceeding fifteen days in the whole; and if he has no jurisdiction to try the case or commit it for trial, and considers further detention unnecessary, he may order the accused to be forwarded to a Magistrate having such jurisdiction:
Provided that—
(a) the Magistrate may authorise the detention of the accused person, otherwise than in custody of the police, beyond the period of fifteen days, if he is satisfied that adequate grounds exist for doing so, but no Magistrate shall authorise the detention of the accused person in custody under this paragraph for a total period exceeding—
(i) ninety days, where the investigation relates to an offence punishable with death, imprisonment for life or imprisonment for a term of not less than ten years;
(ii) sixty days, where the investigation relates to any other offence, and, on the expiry of the said period of ninety days, or sixty days, as the case may be, the accused person shall be released on bail if he is prepared to and does furnish bail, and every person released on bail under this sub-section shall be deemed to be so released under the provisions of Chapter XXXIII for the purposes of that Chapter;
(b) no Magistrate shall authorise detention of the accused in custody of the police under this section unless the accused is produced before him in person for the first time and subsequently every time till the accused remains in the custody of the police, but the Magistrate may extend further detention in judicial custody on production of the accused either in person or through the medium of electronic video linkage;
(c) no Magistrate of the second class, not specially empowered in this behalf by the High Court, shall authorise detention in the custody of the police.
Explanation I.—For the avoidance of doubts, it is hereby declared that, notwithstanding the expiry of the period specified in paragraph (a), the accused shall be detained in custody so long as he does not furnish bail.
Explanation II.—If any question arises whether an accused person was produced before the Magistrate as required under clause (b), the production of the accused person may be proved by his signature on the order authorising detention or by the order certified by the Magistrate as to production of the accused person through the medium of electronic video linkage, as the case may be:
Provided further that in case of a woman under eighteen years of age, the detention shall be authorised to be in the custody of a remand home or recognised social institution.
(2A) Notwithstanding anything contained in sub-section (1) or sub-section (2), the officer in charge of the police station or the police officer making the investigation, if he is not below the rank of a sub-inspector, may, where a Judicial Magistrate is not available, transmit to the nearest Executive Magistrate, on whom the powers of a Judicial Magistrate or Metropolitan Magistrate have been conferred, a copy of the entry in the diary hereinafter prescribed relating to the case, and shall, at the same time, forward the accused to such Executive Magistrate, and thereupon such Executive Magistrate, may, for reasons to be recorded in writing, authorise the detention of the accused person in such custody as he may think fit for a term not exceeding seven days in the aggregate; and, on the expiry of the period of detention so authorised, the accused person shall be released on bail except where an order for further detention of the accused person has been made by a Magistrate competent to make such order; and, where no order for such further detention is made, the period during which the accused person was detained in custody under the orders made by an Executive Magistrate under this sub-section, shall be taken into account in computing the period specified in paragraph (a) of the proviso to sub-section (2):
Provided that before the expiry of the period aforesaid, the Executive Magistrate shall transmit to the nearest Judicial Magistrate the records of the case together with a copy of the entries in the diary relating to the case which was transmitted to him by the officer in charge of the police station or the police officer making the investigation, as the case may be.
(3) A Magistrate authorising under this section detention in the custody of the police shall record his reasons for so doing.
(4) Any Magistrate other than the Chief Judicial Magistrate making such order shall forward a copy of his order, with his reasons for making it, to the Chief Judicial Magistrate.
(5) If in any case triable by a Magistrate as a summons-case, the investigation is not concluded within a period of six months from the date on which the accused was arrested, the Magistrate shall make an order stopping further investigation into the offence unless the officer making the investigation satisfies the Magistrate that for special reasons and in the interests of justice the continuation of the investigation beyond the period of six months is necessary.
(6) Where any order stopping further investigation into an offence has been made under sub-section (5), the Sessions Judge may, if he is satisfied, on an application made to him or  otherwise, that further investigation into the offence ought to be made, vacate the order made under sub-section (5) and direct further investigation to be made into the offence subject to such directions with regard to bail and other matters as he may specify.

Index of all Bail matters is here.