According to WCVB News out of Boston:
Emergency crews responded to reports of an ammonia leak inside a warehouse in Boston’s Seaport District on Wednesday.
The incident was reported just before 6 p.m. at Stavis Seafoods, at 7 Channel St., and workers in the area were told to shelter-in-place or walk to D Street.
Streets surrounding the warehouse have been blocked off by police.
Boston fire officials said crews have been unable to reach the ammonia shutoff inside the large facility.
— Breaking911 (@Breaking911) March 23, 2016