NEW YORK, NY March 05, 2008 —Demolition on the east Harlem building that collapsed yesterday has begun - and is expected to last a few days. But it will be halted during rush hours tonight to ensure safety.

REPORTER: Forensic engineers with the Department of Buildings are investigating the cause of the collapse but Commissioner Patricia Lancaster defended the work of inspectors who issued five violations to the owner but didn't predict the dangers.

LANCASTER: Buildings are not maintained and violations are written often. And the number of times that that makes them fall down is not very many. So something happened here and we are trying to figure out what that is.

REPORTER: Lancaster says it will take weeks to determine an official cause but says the DOB is looking into la law that would require owners of vacant buildings to file a structural integrity report.

A spokesperson for the owner, Jared Kushner says as soon as they detected structural problems they notified the city - but are thankful no one was hurt in the collapse.