A fire that broke out at apparel retailer Gap Inc's distribution center in New York last week was intentionally set, the New York State Police said on Tuesday.

"The ATF National Response Team has concluded that the fire was incendiary in nature. This means that the fire was intentionally set," the state police said.

Last week, the retailer reported the incident at its facility in Fishkill, New York, its primary distribution center for the U.S. Northeast. The company said that all employees were safe.

The state police and the ATF said they were continuing the investigation.

Gap, which reported a 3 percent fall in August comparable sales last week, said it was working to mitigate the impact of the fire on its business.