TOLEDO, Ohio (AP) — Officials in northeast Ohio say an employee error caused a chemical reaction that led to a tank rupture at an industrial facility earlier this week. All remaining evacuation orders have been lifted.

Toledo Mayor Wade Kapszukiewicz said Friday that the tank at MC Tank Terminal finished venting late Thursday night, allowing a hazardous materials team to enter the site and check safety levels.

Toledo Fire and Rescue Battalion Chief Blake Molnar said officials believe the site is safe.

The rupture occurred late Tuesday night at the facility owned by MC Tank Transport. The tank contained glycidyl methacrylate, an industrial chemical used to improve the performance of certain plastics, paints and coatings, according to the company.

Kapszukiewicz said an employee introduced a temperature level into the tank while attempting to transfer the liquid, triggering a chemical reaction. The company has accepted responsibility for the incident, according to the mayor.

Hundreds of people were initially evacuated from their homes, and 57 people were treated at hospitals.

The mayor said there was no fire or explosion. He said the chemical reaction had run its course, allowing the community to begin returning to normal.

The investigation remains ongoing, and officials have additional questions to resolve, Kapszukiewicz said.