At least 21 workers were killed after the coal mine they were working in collapsed in China’s Shaanxi province on Saturday, Xinhua reported. Eighty-seven workers were reportedly at the site when the incident occurred.

Preliminary reports had pegged the toll at 19 and the number of those rescued at 66. Rescue personnel found two more bodies on Sunday, taking the toll to 21.

Investigators are looking into what could have caused the collapse at the Baiji Mining-run Lijiagou coal mine.

The National Coal Mine Safety Administration has issued notices to several mining firms in Shandong and Henan provinces and asked them to halt operations for inspections, Reuters quoted a report as saying.