A decades-old fight about the direction of one of New York’s most prominent Hasidic Jewish groups tipped into chaos this week, when a faction of the group clashed with the police over a tunnel that had secretly been built to the movement’s main synagogue, one of the most significant religious sites in the city.

The tunnel, a passageway between the headquarters of the group, the Chabad-Lubavitcher movement, and at least one adjacent property, was first discovered late last year, according to local news reports. But on Monday afternoon, after a cement truck was brought in to fill it, some Hasidic men attempted to block that effort.

The police were called, and officers said they found a group of men breaking through a wall of the prayer space that led to the tunnel. After a resulting confrontation, which included skirmishes with officers, nine people were arrested, according to the Brooklyn district attorney’s office.

Motti Seligson, a Lubavitcher spokesman, described those who had created the tunnel as a group of “extremist students.”

“This is, obviously, deeply distressing to the Lubavitch movement, and the Jewish community worldwide,” he said in a written statement.

The conflict took place at 770 Eastern Parkway in Crown Heights, Brooklyn, the movement’s global headquarters, which is often referred to simply as 770.