U.S. law enforcement authorities were on Friday investigating letters or packages containing suspicious powders sent to several hotels and other locations near the site of Sunday's Super Bowl in New Jersey and New York City.

"The Joint Terrorism Task Force and Hazard Materials units have responded to several locations that have received a suspicious letter and substance," the New Jersey State Police said in a statement Friday afternoon, two days before the much-anticipated Super Bowl opens.

"There are no reported injuries at this time, and the locations are being secured," said the police, adding that the situation is being "thoroughly investigated."

The authorities have not identified the sites that have received the packages or why they were considered suspicious. Media reports suggested some of the suspicious letters contain white powder.

In New York, authorities were also investigating a letter sent to the Manhattan office of former New York City Mayor Rudy Giuliani that contained white powder, law enforcement officials told CNN.

Till now, seven suspicious letters or packages has been reportedly sent to hotels and other sites near Sunday's Super Bowl in East Rutherford, New Jersey, including six in the north New Jersey area and one in Manhattan, New York.

Federal officials told NBC that one letter examined was found to contain only baking soda.

Local WABC TV reported that seven sites in New Jersey, including six hotels and one post office have received suspicious packages, and some other suspicious packages were intercepted before they were delivered to more local hotels.