18 U.S.C. § 3187: Provisional arrest and detention within extra­territorial jurisdiction

The provisional arrest and detention of a fugitive, under sections 3042 and 3183 of this title, in advance of the presentation of formal proofs, may be obtained by telegraph upon the request of the authority competent to request the surrender of such fugitive addressed to the authority competent to grant such surrender. Such request shall be accompanied by an express statement that a warrant for the fugitive’s arrest has been issued within the jurisdiction of the authority making such request charging the fugitive with the commission of the crime for which his extradition is sought to be obtained. No person shall be held in custody under telegraphic request by virtue of this section for more than ninety days.