The Howard Street tunnel reopened Thursday night after it was closed by a train derailment Monday.
CSX officials said normal train operations resumed at 8 p.m. Thursday.
A 13-car CSX freight train derailed early Monday morning inside the tunnel. Twelve derailed train cars were empty. One car was filled with a "possible flammable liquid" later identified as acetone, used in nail polish remover, according to fire officials. No hazardous materials were released during the incident.
CSX is investigating the cause of the derailment.