U.S. authorities say two former New York City college students have been indicted on terror charges accusing them of plotting to help the Islamic State group.

Munther Omar Saleh and Fareed Mumuni have been in custody since June. Federal prosecutors in Brooklyn announced on Tuesday a grand jury had returned an indictment.

Prosecutors say the 21-year-old Saleh had researched recipes for homemade explosives and looked up city landmarks on the Internet. They also say he and the 20-year-old Mumuni discussed how to build a pressure cooker bomb.

Their defense attorneys haven't responded to messages seeking comment on the indictment. An attorney previously denied Mumuni is an Islamic State convert and said he has a clean record.

An arraignment is set for Aug. 20.