Cesar Sayoc, the Florida man accused of mailing bombs to former President Barack Obama, former Secretary of State Hillary Clinton and other leading critics of President Donald Trump, was ordered held without bail Tuesday during his first appearance in federal court in New York.

Sayoc, 56, is "a serious risk of danger to the public and a flight risk," assistant U.S. Attorney Jane Kim told Magistrate Judge Robert Lehrburger during a hearing in U.S. District Court in Manhattan, according to NBC News.

Lehrburger, whose decision to hold Sayoc without bail was not opposed by defense lawyers, ordered him to be brought back to court next Monday.

Sayoc was arrested on Oct. 26 in South Florida in connection with pipe bombs mailed to prominent Democrats and other people critical of Trump, including former Vice President Joe Biden, billionaire Democratic donor George Soros, former CIA Director John Brennan and actor Robert De Niro. None of the bombs exploded.

Sayoc's social media feeds were loaded with pro-Trump and anti-Democrat memes, along with apparent threats against people. Sayoc also drove a van plastered with similar propaganda. Trump has called Sayoc "insane."

Sayoc faces up to 48 years in prison if convicted in the case.