They are questioning whether an employee who closed the HSBC branch Friday night deliberately didn't set the alarm, allowing burglars to cut a hole in the roof and enter the vault, according to the official, who was briefed on the investigation.
Around 6 p.m. Friday night, the HSBC's command center notified the branch manager that the alarm had not been set.
A half hour later, the employee and the manager went back to the bank but couldn't set the alarm for the entire bank because the sensor alarms in the vault kept tripping, according to the official.
The command center advised that they set the alarm for the rest of the bank and check back on the vault on Monday, when the timer on the vault would unlock, according to the official.
On Monday morning, an employee opened the vault and found a hole in the ceiling and multiple safe deposit boxes thrown around, the official said.
Investigators are now looking into whether the suspects may have already been in the vault by the time the bank manager returned to set the alarm, the official said.
The robbers made off with $280,000 in cash and an unknown number of safety deposit boxes, according to NYPD Detective Hubert Reyes.
Security cameras at the branch did not catch the perpetrators, according to Reyes. The NYPD could not comment on whether the cameras weren't working or whether they weren't turned on but said that it will be a part of the investigation.
Authorities have been collecting evidence from the scene and found a ladder on the roof, Reyes said.
The bank is in the predominately Orthodox Jewish neighborhood of Borough Park, which tends to be quieter on weekends as residents observe the Sabbath.
The robbery is being investigated by the FBI and NYPD Joint Robbery Task Force.