Chicago Sun-Times: The former Chicago Tribune Freedom Center is being torn down to make way for the casino. Some white material is still floating up the river.

Looking out her window early Saturday afternoon, Michele Berman noticed something that looked like black-mesh netting across the river, partially blocking demolition of the former Chicago Tribune’s Freedom Center printing plant.

Within a couple of hours, she said, a wall collapsed, sinking the netting into the Chicago River while debris and a sizable amount of white substance dumped into the water.

“My daughter looked at [the netting] and said, “What is that going to hold?’ Literally, two hours later it all dumped into the river,” Berman said.

The material formed a large “white cloud” that floated up the river, Berman said. “It looked like packing peanuts, but I don’t know what it is.”

On Wednesday, the material was seen farther north on the river.

The former Tribune property is being torn down to make way for Bally’s Chicago Casino. Since the weekend accident, the demolition has been on hold.

State and local officials are still investigating the matter.

Bally’s and its contractor, Chicago Community Builders Collective, said in a statement that the white material was perlite, used in building insulation, and that it was not toxic.

“We regret this incident occurred and have worked diligently to clean up the non-toxic material from the river,” the companies said. “We will respond quickly to any additional debris reports while making every effort to prevent future incidents as demolition continues.”

The Metropolitan Water Reclamation District, which is responsible for the Chicago area’s sewer system and protection of the river, continues to investigate the incident to determine if there are any violations. The companies are responsible for all the cleanup, a district official said.

City of Chicago officials have also been on the scene as well as the Illinois Environmental Protection Agency. In a statement, the city buildings department said it “has required the contractor to prepare a corrective action plan for the continued demolition.”

Michael Goldwater, who lives nearby and is a member of a River North neighbors’ group, said he was alarmed by the incident.

“My concern is that I want to make sure they understand how this happened, how to remediate and, more importantly, how to prevent it from happening again,” Goldwater said.

For Berman, she wants to know what fell in the river and whether steps are being taken to make sure there are no other accidents.

Before demolition began, Berman said she attended a community meeting held by the city to explain that the Freedom Center teardown is considered an “environmentally complex” demolition.

“They all assured us they were keeping their eyes on it,” Berman said, referring to Chicago officials.

Residents’ reaction to the mishap “demonstrates that people really care about the river,” said Margaret Frisbie, executive director of advocacy group Friends of Chicago River.