Students are heading back to class a day after an emailed threat triggered a shutdown of all public schools in the Los Angeles area.

School buses are rolling Wednesday morning and parents are dropping off children at campuses in the nation's second-largest school district.

The decision Tuesday to close the district with 640,000 students came after a school board member received an email threatening a large-scale attack.

District Superintendent Ramon Cortines says he ordered the closure as a precaution.

New York City schools received a similar threat but officials there concluded that it was a hoax.