The Beth Hamedrash Hagodol synagogue was largely destroyed in a massive fire Sunday night. View Full Caption DNAinfo/Allegra Hobbs

LOWER EAST SIDE — The fire that tore through a historic Lower East Side synagogue Sunday night was deliberately set, according to the NYPD's Chief of Detectives.

►UPDATE: 14-Year-Old Boy Charged With Setting Fire to LES Synagogue, Police Say

Police had reviewed surveillance footage of three young people running from the area surrounding the Beth Hamedrash Hagodol synagogue around the time of the fire, the 7th Precinct's Deputy Inspector told DNAinfo New York Monday, but considered it too early to determine whether there was any criminality involved.

The NYPD now believes the fleeing teens likely caused the blaze, said Chief of Detectives Robert Boyce.

“The synagogue fire in the 7th precinct, we do think it’s arson, a purposeful fire," said Boyce at an unrelated news conference in the Bronx on Tuesday, adding police were now seeking to arrest those responsible.

"We were able to recover video. Initially, witnesses said they saw a young group running from the location. We have that video. We’re looking at it now. It’s very probative. We looking forward to making an arrest in that case.”

The FDNY would not confirm Boyce's comments, but said the cause of the fire remains under investigation.

The landmarked structure was mostly reduced to rubble by the massive fire — the ceiling and some of the walls collapsed, leaving a 15-foot pile of debris on the first floor of the synagogue, though the library basement remained largely preserved.

The Department of Buildings and the Landmarks Preservation Commission are still in the process of assessing the damage, representatives for both agencies said.