Noelle Velentzas and Asia Siddiqui, who are also former roommates, had been "obsessed with pressure cookers since the Boston Marathon attacks in 2013" and made jokes alluding to explosives after receiving one as a gift, according to a criminal complaint.

The complaint unsealed in federal court in Brooklyn names the two women as the targets of an undercover investigation into a homegrown terror plot.

After a brief court appearance where they spoke only to say they understood the charges against them, the women were held without bail. Velentzas wore a hijab and a dark dress, and Siddiqui was wearing a green T-shirt with a long-sleeved black shirt underneath and a dark long skirt.

Officials noted that the women repeatedly expressed support for violent jihad during conversations with an undercover investigator who was wearing a wire.

The complaint said that at the time of her arrest, Siddiqui was "in possession of multiple propane gas tanks, as well as instructions for how to transform propane tanks into explosive devices."

Authorities also wrote that since 2014, the pair had plotted to build an explosive device to use in a terrorist attack on American soil. They "researched and acquired some of the components of a car bomb, like the one used in the 1993 World Trade Center bombing; a fertilizer bomb, like the one used in the 1995 bombing of the federal building in Oklahoma City; and a pressure cooker bomb, like the one used in the 2013 Boston Marathon bombing."

Multiple arrests in last several weeks

The arrests came on the same day that another U.S. citizen was brought back from Pakistan to New York to face charges that he supported a conspiracy to kill Americans. Muhanad Mahmoud Al Farekh appeared Thursday in Brooklyn federal court and was held without bail. His lawyer did not comment.

Farekh's arrest followed another New York case announced last month in which a US Air Force veteran was accused of scheming to travel to Syria to join the Islamic State group. Tairod Pugh, 47, had recently been fired from his job as an airplane mechanic. Prosecutors said he traveled from Egypt to Turkey to ultimately cross the border but was turned away.

Also in March, three other men pleaded not guilty in Brooklyn federal court to terrorism charges in a plot to travel from New York to Syria via Turkey in a bid to join the Islamic State group.

av/gsw (AFP, AP)