Firefighters responded to 559 Commercial St., where a crane fell over around 11:30 a.m., spilling an estimated 200 gallons of diesel fuel and hydraulic fluid and putting a major dent in a pickup truck across the street.
The Boston Fire Department reports the driver and a passerby were transported to Mass. General for evaluation.
A BFD hazmat crew is on scene. Fire officials say Commercial Street could be shut for most of the day as the mess is cleaned up.