Hazmat crews responded to the scene of a 300- to 400-gallon sulfur dioxide leak in Salt Lake City that affected 56 people on Wednesday morning.

According to the Salt Lake City Fire Department, the substance leaked from a rail car at Thatcher Chemical, 1905 Fortune Road, about 8:40 a.m.

SLCFD tweeted that 43 people were treated for “potential symptoms" of exposure to the sulfur dioxide; two were taken to a local hospital. The condition of those affected is not yet known.

According to the Environmental Protection Agency, “short-term exposures to” sulfur dioxide “can harm the human respiratory system and make breathing difficult.”

The leak has been stopped; all those affected have been treated.