Are there any proofs that Fajr has two Adhans?

For Fajr prayer, there are two Adhans: the first is before the entry of Fajr time, to alert people to its approaching arrival, benefiting those who are asleep, those performing night vigil, and those who wish to eat suhoor. The second is after the entry of Fajr time, to announce the beginning of the prayer time. Clear prophetic hadiths have indicated this, among them the saying of the Prophet, peace and blessings be upon him: "Let not the Adhan of Bilal prevent anyone of you from his suhoor, for he calls the Adhan at night, so that your worshipper may return [to rest], and your sleeper may be awakened, and not to say that Fajr or dawn has arrived." And his saying: "Indeed, Bilal calls the Adhan at night, so eat and drink until Ibn Umm Maktoum calls the Adhan."