An anonymous tip led detectives to identify the suspects, who were already in custody in the Denver County Jail.
7NEWS has previously reported on two other Denver cases concerning Graf and Howard.
In November 2013 they were arrested by Denver police following a raid of an apartment near Interstate 25 and Evans Avenue. In that apartment, investigators said they found suspected methamphetamine, suspected heroin, five Social Security cards, more than $1,000 cash, a .38-caliber handgun, body armor, televisions, power tools and 75 computers. They also found an Aurora Public Schools security guard uniform.
Court documents obtained by 7NEWS in November indicated that Graf and Howard are also suspected of stealing a $65,000 pickup from Phil Long Ford.
Then, six months later, in May, 7NEWS reported that Graf and Howard were arrested for allegedly cutting through the wall of a storage unit in southwest Denver and stealing power tools.
When police executed a search warrant in an adjacent unit, they recovered more than 96 items, from various people. The investigators also found an old license that was stolen in 2007 had been used to lease the unit.
Graf and Howard have since been transferred to the Huerfano County Jail where they are awaiting court proceedings in other cases.