Police are investigating threats against dozens of schools this week in seven U.S. states. Searches failed to find bombs or other dangers. Threats were called in to at least 26 schools in New Jersey on Tuesday. Most were to schools in suburbs of New York City, police said. Other threats were called in Tuesday to schools in Maryland, Iowa, Massachusetts, Delaware, Arizona and Florida. Wednesday brought more bomb threats to schools in Delaware and Arizona. The threats come at a time polling shows Americans worried about terrorist attacks. New Jersey police officials said voices on the threatening phone calls sounded altered by computers. The calls were traced to Bakersfield, California, police said. At Clifton High School, a voice mail warned of a bomb. A separate call warned of a “mass shooting” at the school later on Tuesday, said Sgt. Robert Bracken of Clifton Police Department. The responses to the threats varied, according to news reports. Some schools moved students to other buildings while officials searched the threatened schools.