Two twin brothers from the Bronx, one of them a teacher, were arrested by federal authorities Thursday for alleged possession of bomb-making materials, sources said.

Christian and Tyler Torro, both 28, were arrested Thursday, sources said.

Federal authorities said they were in possession of a jar of gun powder and an imitation pistol, sources said.

NBC New York published the following details:

Christian Toro was a teacher at a high school in Harlem, where, on Dec. 4, a bomb threat was called in and a student was later arrested for the threat. Toro resigned from the school shortly afterward, authorities said.

After he resigned, his brother Tyler returned Christian’s school-issued laptop to the school. A technical specialist there found copy of a book providing insturctions on how to assemble bombs.

Law enforcement was alerted, and they went to Christian Toro’s Bronx apartment to interview him on Feb. 8; there, he and Tyler and another female relative told the agents that he hasn’t meant to download the explosives manual to the laptop. He said he’d been researching the 2013 Boston Marathon bombings when he came across the book.

Christian Toro said he only looked at the book’s table of contents.

On Wednesday, FBI went to speak with several students at the Harlem school, and the agents learned that at least two students had gone to Christian Toro’s apartment in the Bronx to break apart fireworks and store the gunpowder in containers. Christian paid the students $50 an hour for their work, the complaint alleges.

A search warrant was executed at Christian Toro’s apartment Thursday, and law enforcement found in his bedroom 20 pounds of iron oxide and five pounds of aluminum powder, which form thermite when combined; five pounds of potassium nitrate; two pounds of confectioner’s sugar, which can be used as fuel for making explosive devices; a glass jar of a black explosive powder, which can explode when properly confined and lit with a fuse; a cardboard box of firecrackers; a plastic container of apparent thermite; a small container of potassium nitrate; and a bag of metal spheres, which can be used as fragmentation and released as projectiles.

FBI agents also found on the kitchen table a diary filled with handwritten pages. The front of the diary said it belonged to Tyler Toro.

Among the writing in the diary, according to the complaint, were statements such as:

“When you find out I threw away all evidence [of operation code name ‘Flash’] I could find in your room, I hope this doesn’t turn into a scene from ‘Goodfellas'”

“We are twin Toros strike us now, we will return with nano thermite”