GRAFTON, Wis. (CBS 58) -- A roof partially collapsed Friday, Nov. 14 at a construction site in the area of Port Washington Road and Lakefield Drive in the Town of Grafton, sending three workers to the hospital, according to the Ozaukee County Sheriff's Office.

The incident happened at around 9:45 a.m. at a storage condominium unit under construction.

Workers were securing wooden roof trusses when the north wall bowed and the roof partially collapsed, the sheriff's office says. The three workers fell approximately 16 feet, and one became trapped under the debris.

The Ozaukee Central Fire Department responded and cut through the trusses to free the trapped worker. All three injured workers sustained non-life-threatening injuries and were transported to Froedtert Hospital in Wauwatosa.

The Town of Grafton Residential and Commercial Building Inspectors, along with OSHA representatives, responded to inspect the construction site. The cause of the collapse is still being determined.