HOUSTON --After a series of unsolved arson cases, investigators tonight have released a key piece of evidence, hoping you can help them catch the serial arsonist. According to the Houston Fire Department, there have been 30 fires in southwest Houston in the last 17 months. The most recent was this weekend blaze near Woodway and Ross. The fire department released video of a suspect and his vehicle. Fire investigators say the suspect appears to be a white man shorter than 6 feet tall with dark hair and a medium to heavy build. He appears to have an unsteady gait or a slight limp when walking. He may have had some burns to the face or hands. Investigators are also looking for a Chevrolet Dually 3500. That truck has two rear wheels on each side. There may be a dent between the right rear fender and passenger side door. Authorities are also looking for a 1997 dark Lexus car. If you know anything, call crime stoppers at 713-222-8477.