The support straps on a utility box that fell from a column and struck a woman at a Red Line station Monday were corroded, an MBTA spokesperson said.

This safety failure prompted an immediate investigation of all MBTA stations, where inspectors looked into the condition of similar equipment, spokesman Joe Pesaturo said.

“Immediately following last night’s incident, the area surrounding the box was cordoned off and an inspection was performed,” Pesaturo said in a Tuesday email. “Subsequently the utility box was safely removed.

“It was determined that the cause of the incident was due to corrosion on the support straps that secured the box to the column.”

This incident, which sent a woman to the hospital with minor injuries, occurred just two months after a 25-pound water-logged ceiling tile fell at the same station, Harvard in Cambridge, nearly striking a rider walking through the area.

MBTA General Manager Phillip Eng visited Harvard station on Monday evening, and “directed that every station be immediately inspected for the presence of these boxes and the condition of the support straps to ensure that they do not pose a hazard,” Pesaturo said.

Inspections are expected to be completed on Tuesday. As of this morning, the Red and Orange Line had been fully inspected, and probes of the Blue and Green Lines were ongoing, Pesaturo said.

“At this point, it was an isolated case,” he said of the utility box corrosion. “While the inspections will continue today on the Blue and Green Lines, it is believed the boxes are present only on the Red Line.”

Eng reached out to the woman, who was standing on the platform when she was struck by the falling equipment, Pesaturo said.

The rider was hit by a supporting brace, after the utility box attached to the column slid to the bottom of the structure, he said.