Casey Kasem -- Elder Abuse Criminal Investigation Targeting Wife Jean

Police are looking into allegations ... Casey Kasem's health may have been fatally compromised when his wife removed him from a convalescent home and took him on a surreptitious, multi-state ride ... and now there's a criminal investigation, TMZ has learned.

Family sources tell TMZ ... Casey's daughter Kerri contacted the Santa Monica Police Dept., claiming her dad is the victim of elder abuse at the hands of Jean Kasem.

Kerri handed over documents which she said showed ... Jean removed Casey from the Berkley East Convalescent Hospital last month. Kerri claims Jean drove to Nevada to find a place to keep Casey away from the family.

Nevada proved fruitless, so Jean drove Casey to Arizona, then back to Nevada and then finally flew him to Washington.

Our sources say Kerri has medical documents showing that during the trip Casey developed a bedsore which then became infected and ultimately life-threatening.

Kasem family sources say the infection could end up being the immediate cause of death -- which looks likely to occur at any time.

Our sources say the Santa Monica PD is currently investigating Kerri's allegations, and Jean is the target.