EAST RUTHERFORD — The suspicious white powdery substance delivered to at least six hotels just miles from MetLife Stadium is believed to be cornstarch, officials said.

The discoveries Friday prompted a major law enforcement response and triggered a security scare two days before the stadium will host the Super Bowl. Hazardous materials units, the bomb squad and federal agents descended on the hotels and two post offices to analyze the substance and search for evidence.

Though investigators believe the off-white substance sent in envelopes is cornstarch, they're awaiting final test results from county haz-mat officials, Jeanne Baratta, the Bergen County Executive’s Office Chief of Staff, said Friday afternoon. The FBI said the substance was deemed to be harmless, but did not elaborate.

“The locations have been secured and initial field screening on the first samples has shown the substance to be within normal values,” a statement from the FBI’s Newark division said.

Additional tests would be conducted at a Trenton lab, but there were no reports of any illnesses from the letters, according to state police.

In Rutherford, Police Chief John Russo said officers were alerted around noon when an employee at the Renaissance Meadowlands Hotel saw an off-white powdery substance while opening mail. Authorities quickly quarantined the woman.

“She was in good health the entire time and there was no need for medical attention,” he said.

Emergency crews talked to the woman through a window during the investigation, Russo said. The county’s hazardous materials team later confirmed the substance was cornstarch.

“We got lucky in that it turned out to be nothing,” the chief said.

Some hotel guests were evacuated on borough buses and brought to the nearby library to keep warm, Russo said. Others on upper floors were told to stay in their rooms while police secured the area.

FBI agents took the letter and were handling the investigation, he added. Police declined to detail what was included in the message.

Police also tracked the letter back to a mail route and delivery driver at the Rutherford post office, where authorities conducted another search, according to the chief. That investigation didn’t turn up any suspicious substances or letters.

Similar reports emerged throughout the day in six towns near the Super Bowl site. Two suspicious letters were discovered at the Courtyard at Marriott and the Quality Inn in Lyndhurst. The letters were "isolated" and no one was exposed to any danger, Police Chief James O'Connor said.

In Wood-Ridge, officials also found a white powdery substance believed to be cornstarch at the post office, according to police.

Wood-Ridge Mayor and State Senator Paul Sarlo said schools were operating normally, but officers were out to ensure a safe dismissal.

"I have the utmost confidence in federal, state and local law enforcement that this will be a very secure Super Bowl," he said outside of the post office late Friday afternoon.

Police and emergency crews also tended to a report of a suspicious letter at the Hilton Hasbrouck Heights on Terrace Avenue and the EcnoLodge motel on Washington Avenue in Carlstadt, officials said. County haz-mat units began receiving reports of the letters around 11:45 a.m.

Another letter was mailed to the 6th Avenue office of former New York City Mayor Rudy Giuliani, the NYPD said. The letter was found to be harmless, but a police spokesman could not immediately say what it contained or if it was related to the others.