The incident happened just after noon in front of Acme Windows on Somerset Street in Plainfield.
Authorities say the 67-year-old woman appeared to be texting when she fell through the open door.
The Plainfield Fire Division extricated the woman from the hole and rushed her to the hospital for treatment of serious injuries.
The access doors were open due to the repair of gas lines in the area.
The victim is listed in serious condition.
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