BROOKLYN - A Brooklyn school went on lockdown Thursday night after police received a call that a parent reportedly opened an envelope containing a suspicious powder.

Police say they arrived at M.S. 839, located at 713 Caton Ave., as a precaution. No one was visibly ill.

According to a New York Post report, a father who is a city housing court judge brought his personal mail to the school's open house and found the powder while opening a letter.

Witnesses say police locked down nearby streets and were not allowing people out of the building as late as 9 p.m.