Exterior walls of a townhouse partially collapsed at a Brooklyn building prompting evacuations, officials say.

The Department of Buildings is investigating the incident at 217 Ninth St.

It happened around 11 p.m. Thursday.

Officials say no one was inside of the three-story townhouse at the time of the collapse, and only the surrounding outer walls fell while part of the building remained intact.

At least 20 residents were evacuated from surrounding buildings near the collapse. They have been ordered to stay away from their homes and are being assisted by the American Red Cross, officials say. 

Orders to demolish the building were placed with the city on April 30.

The Department of Buildings is slapping the owner with a violation for failing to maintain this home.

Demolition of the building could start as early as Friday night.

No one lives in the building and no one was injured, officials say.

The cause of the collapse is unknown.

The owner declined to comment to News 12.