HAMPSHIRE, Ill. (AP) — Authorities say a chemical explosion at a northern Illinois manufacturing plant killed one person and left another critically injured.

Hampshire Fire Protection District Chief Trevor Herrmann says the incident occurred about 10:45 a.m. Friday when two employees at the W. R. Meadows building materials plant in Hampshire were cleaning a tank inside one of the buildings.

Herrmann tells the Chicago Tribune it’s not clear yet what type of chemicals were involved or what might have triggered the accident. He says W. R. Meadows manufactures asphalt and concrete products for building construction.

Hampshire Village Manager Jay Hedges says the explosion caused significant property damage.