LONGVIEW, Washington (From news reports) -- Newly-obtained state records reveal a serious workplace accident at the Nippon Dynawave pulp and paper mill in Longview, months before a tank collapse killed 11 workers in May.

Documents released by the Washington Department of Labor and Industries (L&I) describe a March incident in which hot pulp spilled from a faulty valve, creating a sinkhole that partially submerged an employee. The March incident does not appear to involve the same tank that collapsed more than two months later, unleashing a wave of chemicals.

According to the incident report, a mid-stock drain valve had been plugged since the previous year. When it finally broke free, approximately 2 to 3 feet of hot pulp -- a milky industrial liquid -- flooded the area around a tank. A worker responding to the spill waded into the hot stock, stepped into a sinkhole concealed by the flowing liquid, and "became submerged in hot stock up to his chest," the records state.

The employee was wearing protective gear and was not seriously injured. Labor and Industries classified the event as a "near miss" and a serious accident.

A key question remains unanswered: whether Nippon Dynawave reported the March incident to Labor and Industries as required. State records indicate the agency did not become involved until roughly a month after, when an employee filed a complaint.

Labor and Industries said the March case is still under investigation and that no citations have been issued.

Nippon Dynawave mill handles an array of toxic chemicals and industrial hazards. The take collapse in May is the deadliest industrial accident in state history. It remains under investigation.

Nippon Dynawave did not immediately respond to a request seeking comment on the March incident.