An American citizen detained in Egypt since 2013 died of heart failure following a hunger strike, ABC reported on Tuesday.According to the report, in August 2013 Mustafa Kassem, a 54-year-old New York taxi driver and a father of two, was visiting Cairo and the night before flying back to the US went out to make some shopping and exchange money. He was arrested on the accusation of being involved in the protests against General Abdel Fattah al-Sisi, who roughly a month earlier had removed Muslim Brotherhood leader Mohammed Morsi from office as president. According to several human rights groups, at least several hundred people were killed on that night, August 14, 2013."Last Thursday, he ceased taking liquids and was shortly thereafter transferred to a local hospital, where he passed away today in the late afternoon (local time)," Pretrial Rights International, who represented Kassem, said in a statement."A diabetic with a heart condition, prison officials limited access to necessary medications and medical care for the entirety of his (Kassem's) detention. He remained in pretrial detention for over five years," it added.Kassem reportedly started his hunger strike in September 2018, after being sentenced to 15 years for trying to overthrow the Egyptian government in a mass trial that included over 700 co-defendants. "Dear President Trump: As an American beginning the hunger strike that could leave my two young children without a father and make my wife a widow, I pray that you secure my freedom," he said in letters that he sent to US President Donald Trump and Vice-president Pence.Last month, Secretary of State Mike Pompeo said that he had discussed Kassem's case with his Egyptian counterpart Sameh Shoukry.Following the report of his death, a senior US State Department official told ABC that it's "still premature to talk about" Washington taking action against Egypt for Kassem's death. "We are really concerned about this, and we're going to talk about it," the official added. According to a State Department spokesperson, there are several US citizens currently detained in Egypt."Mustafa Kassem, a US citizen, just died after 6 years in an Egyptian prison. Like 1000s of the country's political prisoners, he should've never been detained. Pompeo must remind Egypt that military aid is legally tied to releasing prisoners, including at least 6 US citizens," US Senator Chris Murphy wrote on Twitter.Kassem was detained in the same prison were Morsi was jailed. The former Egyptian president died of a heart attack after collapsing during his trial in June 2019.