BOSTON -- Officials said a Green line MBTA trolley crash early Tuesday jammed the commute near Cleveland Circle and sent four people to the hospital with injuries.

A trolley on the C Line hit a flatbed truck about 7:15 a.m. as the truck was attempting to cross the tracks on Beacon Street, SmartRoutes reported. The 10-wheel truck was knocked on its side by the impact.

"Four people including the driver of the truck were taken to a local hospital with neck and back injuries," MBTA spokeswoman Lydia Rivera said.

The truck driver was taking a U-turn on Beacon Street and did not yield to the trolley, which was traveling about 10 mph, Rivera said.

New traffic lights at the busy Coolidge Corner intersection were not on.

"There are visible signs (that say) 'Yield to the Trolleys' and, obviously, lights along the right away and people definitely need to be cognizant of that," Rivera said.

The truck straddled the trolley tracks for three hours, causing major traffic congestion during the morning commute.

The reason it took so long to clear the scene was because the truck had to be pulled upright before it could be moved.

"There was certainly some amount of fuel that was spilled," a firefighter said, and that caused a safety hazard.

A wrecker finally removed the truck while T commuters were bused between Coolidge Corner and St. Mary's as a result of the accident. The trolley was damaged but the tracks were fine. By late in the morning, all the trolleys were back on a normal schedule.