MBTA Transit Police on Saturday said that a large piece of concrete was thrown at a bus window in Quincy, and another large group surrounded another MBTA bus on the Franklin Park Loop.

The bus vandalism in Quincy was reported around 3 p.m. Friday in the area of Hancock and Coddington streets, MBTA Transit Police said.

A large piece of concrete was thrown at the bus, causing its window to “spider web” crack, police said. The MBTA removed the bus from service, which caused service delays.

Then, early Saturday morning, around 1:30 a.m., a large disorderly group surrounded an MBTA bus on the Franklin Park Loop, police said. The group was “refusing to allow” the bus to move and the bus driver and passengers “felt threatened,” police said.

Several Transit Police units responded and dispersed the group. That bus resumed normal service.

Transit Police are investigating the bus vandalism, officials said.

This is a developing story. Check back for updates as more information becomes available.

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