FORT RECOVERY — Mercer County Sheriff Jeff Grey asked for extra help from a specialized state investigation unit in hopes of solving the double murder of a man and his daughter.Grey asked the Ohio Bureau of Criminal Identification and Investigation's Special Investigation Unit to lend investigators to the case involving the slayings of Robert F. and Colleen M. Grube. Both were found dead inside Robert Grube's home Wednesday. Robert Grube's daughter-in-law, Cassandra Grube, found them bound and shot inside the house. Cassandra Grube drove to the house after family members were unable to get a hold of the two.Mercer County deputies and state investigators are working extra hours in hopes of solving the case, Grey said. Auglaize County Sheriff Al Solomon has sent deputies to Mercer County to handle routine calls to free up more deputies for the investigation, Grey said. Cassandra Grube found the two bound with duct tape inside their home at 2216 Burrville Road, three miles east of Fort Recovery in a rural setting surrounded by farmland. Investigators found items tossed around rooms in the house as if the person or people who killed the two were looking for something, Grey said.There also were no immediate signs of forced entry to the house, Grey said. The slayings happened sometime after 5 p.m. Tuesday when Colleen Grube left her sister-in-law's house, where she babysat, but before 9 a.m. Wednesday when the bodies were found, Grey said. There have been no arrests or suspects reported and investigators are trying to determine a motive.Colleen Grube, 47, was caregiver and housemate of her father, Robert Grube, 70, who used a wheelchair. Funeral services were held Monday for both at Mary Help of Christians Catholic Church in Fort Recovery. They were to be buried in St. Joseph's Cemetery.Both were graduates of Fort Recovery High School, and Robert Grube served in the Navy during the Vietnam era. He also was a past president of the Mercer County Chamber of Commerce. You can comment on this story at www.limaohio.com.