MAPLEWOOD • The November death of a convicted art thief was ruled a homicide this week after the St. Louis County medical examiner completed a study of the man's brain.

Donald Rasch, 50, was found unconscious Nov. 12 at his home in the 2500 block of Bredell Avenue. He died on Nov. 16 at a hospital.

Police and the medical examiner's office aren't revealing the cause of death, but say it's now classified as a homicide. On Wednesday, Lt. Mark Griffin of the Maplewood Police Department said detectives are still investigating the case and have made no arrests.

In November, police said there were no signs of a break-in or struggle inside Rasch's home. He did not have any outward signs of injury, police said. And an autopsy was inconclusive, so authorities were awaiting toxicology results.

The medical examiner's office signed off on his death certificate on Monday, ruling it a homicide, said Suzanne McCune, forensic administrator for the St. Louis County medical examiner's office. The medical examiner, Dr. Mary Case, made that decision after conducting the brain exam.

Rasch pleaded guilty in 2005 of conspiracy to transport stolen goods in interstate commerce, admitting that he and another defendant stole 133 pieces of artwork valued at up to $4 million in June 2002.

He was sentenced to two years in prison in that case. He also pleaded guilty of one count of making a false statement in 2007 in a case involving art stolen from a store in Bridgeton.