Three Bronx High School of Science students were held up at gunpoint near school Monday afternoon, officials say.

Police say the three students were a few blocks from the school during their lunch period when an armed man in his 30s approached them and robbed them of an iPod, a school ID and a MetroCard.

No one was hurt, according to police.

The students returned to school and reported the incident. Administrators instituted a shelter drill, and no one was allowed into or out of the school for about 20 minutes, principal Jean Donahue told parents in an email.

After police gave the all-clear, the school day resumed normally.

Police are looking for the suspect and say the weapon he was carrying may have been a pellet gun.

Students are permitted to go off campus during lunch or free periods, but Donahue urged parents to remind their children that "they will be safest when they remain on campus during the school day."

More than 3,000 students from across New York City attend the specialized high school, located in the Bedford Park neighborhood.