Resident Ji Zhang reported the issue to the local police.
"The property management doesn't have the right to seal the door," Zhang told Reuters.
Residents shared news and information in online groups before approaching authorities.
"The first request we have is to have a formal, legitimate document to say that ok, you are in a high-risk area, you have to quarantine," said Zoe Zhang, another resident of the building.
"If not, then they should not, A, lock down the main door and, B, if anybody has any emergency, please let us know."
Neighborhood committee staff were unable to provide legal documents supporting the measures, and the restrictions were removed.