The MBTA is investigating an escalator malfunction at the Back Bay Station in Boston on Sunday night that injured multiple people.

In a statement, the agency said the incident involved the escalator from the Amtrak/Commuter Rail platforms to the street-level lobby of the station.

Boston EMS said multiple units responded to the MBTA station shortly after 6 p.m., confirming nine people were injured and taken to local hospitals for treatment.

It was not immediately clear why the escalator malfunctioned and officials have not said what happened. The MBTA said the escalator will remain out of service while the incident is thoroughly investigated, and signs were posted late Sunday night saying “Do not enter.”

A representative for KONE, the company that inspects the escalators, said it is “working closely with the MBTA and other appropriate authorities to gather the facts and determine what may have caused the incident that occurred at the Back Bay station Sunday, and our thoughts go out to those who sustained injuries.”

Source: NBC10 Boston