Metro has found that the Foggy Bottom Station escalator collapse last month was caused by an object that was lodged under the top comb plate of the conveyance, according to an investigation.

The plate broke and displaced a step, which then wedged under another plate at the bottom of the escalator. The wedged step broke four other steps, according to a report on the Feb. 18 incident to be presented to the safety committee of the Metro Board of Directors this week. Neither the report nor Metro officials have specified what the object was, but one official said it was not part of the escalator.

As a result of the malfunction, Metro is examining the configuration of other escalator models for the potential for similar problems, and has also asked the independent consultant Vertical Transportation Excellence (VTX) to review the investigation findings.

The accident caused a gaping hole in the ascending staircase during the morning rush hour, and people on board the escalator narrowly escaped falling in. It came less than four months after another Metro escalator raced out of control on Oct. 30, injuring six people.

Metro General Manager Richard Sarles ordered a system-wide escalator inspection last year that uncovered serious maintenance deficiencies, and last month the agency revealed that escalators are breaking down more often and repairs are taking longer. Sarles predicted this month that it will take years to meet Metro’s goal of keeping more than 90 percent of escalators operating.