Bratton said Friday that some of the stolen property has been recovered.
Five suspects with hammers entered the store at the corner of Fifth Avenue and 52nd Street at about 12:30 p.m. Thursday and smashed open a glass display case. Police said they made off with 16 watches worth more than $700,000.
Investigators have been reviewing security video. Police said some suspects wore masks and all had gloves on.
Police believe the bandits were involved in other similar robberies.
The heist occurred as football fans were flocking to midtown Manhattan for festivities related to the Super Bowl in New Jersey on Sunday.