A law enforcement source says items belonging to two alleged victims of Philip Markoff were found in his apartment.
The Boston medical student is charged with killing one masseuse who advertised on Craigslist and robbing another.
The source would not confirm an ABC News report that the items found by police included the victims' underwear.
Investigators are looking into gambling as the possible motive for the robberies. The law enforcement source says Markoff was a "frequent visitor" to Foxwoods casino in Connecticut.