The FBI is investigating reports about several mysterious nighttime drone flights that have recently occurred across central New Jersey and has asked the public for help. Witnesses have spotted a cluster of what appears to be drones — larger than those typically used by hobbyists — as well as a possible fixed-wing aircraft flying in several areas along the Raritan River since Nov. 18. It’s not clear why the flights happened or who was flying the devices, but federal and state officials stress that there currently is no known threat to public safety. The flights have raised questions in part because they took place near the Picatinny Arsenal, a U.S. military facility, and over President-elect Donald Trump’s golf course in Bedminster.