Sheikh Yusuf Al-Qaradawi states that: “If a person is sure that the timing of Fajr is accurate and confirmed without any doubt according to the local standards, then it is mandatory to stop eating or drinking immediately. Even if there is food or drink in one’s mouth, he is not allowed to eat or drink it, but has to spit it out.
However, if he knows that the adhan is raised few minutes earlier, or even if he doubts the timing, then he has the right to drink or eat until he makes sure of the accurate timing of the Fajr. Nowadays it is easy to know the time through several methods such as watches and Ramadan calendars.
A person asked Ibn `Abbas (may Allah be pleased with him), “I have suhur, but if I have doubt I stop.” Ibn `Abbas said to him: “As long as you are not sure about the Fajr time you can continue eating.”
Imam Ahmad (may Allah bless his soul) is reported to have said: “If a person doubts the time of Fajr, he should keep eating until he is sure it’s Fajr time.”
Imam An-Nawawi (may Allah bless his soul) also said: “The Shafi`i jurists are unanimous that it is allowed to eat if you are in doubt about the Fajr time, because Allah the Almighty has allowed eating and drinking at the night of fasting until the Fajr time is accurately determined. The person in doubt could not determine the time of Fajr, so it is allowed for him to eat until he is sure about the adhan of Fajr. Almighty Allah says: “…and eat and drink until the white thread becometh distinct to you from the black thread of the dawn.” (Al-Baqarah 2:187)
Therefore, I conclude that stopping eating or drinking some time before the Fajr has no basis in the Qur’an or Sunnah, and it is a kind of extremism in religion as it contradicts the Prophetic instructions of delaying the suhur.”