Philadelphia Fire Department deputy chief Charles Johnson speaks to reporters late Tuesday afternoon about a carbon monoxide leak at an apartment building at 48th and Chester (Photo by West Philly Local).

A man has died after a suspected carbon monoxide leak this afternoon at an apartment building at 48th and Chester.

The building, which includes 40 units, has been evacuated and will likely stay closed overnight. No one else was hospitalized, according to Charles Johnson, a deputy chief with the Philadelphia Fire Department.

Work was being done on the heating system in the building, according to Johnson, before the leak was discovered.

Someone from the building called 911 when the man was found unresponsive. When fire department officials arrived at the scene they discovered high levels of carbon monoxide in the building. The investigation is underway.