Federal officials have not released details about the alleged plot. The juvenile remains in custody, and a federal judge will decide whether the suspect will be tried as an adult.

U.S. Rep. Beth Van Duyne, a Texas Republican seeking reelection, said her security has been strengthened. “I don't discuss publicly what we do with security,” she said, adding that her office had been enhancing precautions for months because of what she described as legitimate threats.

Van Duyne said she understood the suspect was inspired by ISIS but cautioned that investigators were still working to establish details. She also suggested the suspect may have been radicalized by conservative opposition to political issues involving Muslims. Authorities have not publicly confirmed a motive.

Self recently criticized plans to expand a mosque in McKinney. Gov. Greg Abbott, in a statement Thursday, praised federal authorities for stopping what he called a terrorist threat and said the state would combat radical Islam.

Van Duyne said she received death threats in 2015, when she was Irving’s mayor and supported a City Council resolution backing a proposed state bill to ban Sharia law in Texas. She said one person who threatened her was later jailed for a murder in Colorado, underscoring why threats against public officials must be taken seriously.

Nine North Texas members of the U.S. House are seeking reelection, putting them on the campaign trail during a period when Van Duyne says security concerns have grown. Investigators have not disclosed further information about the arrest or the alleged plan.