Two officers allegedly took "inappropriate" photos after discovering Nicole Smallman and Bibaa Henry's bodies in north-west London.
The Team GB sprinter and her partner Ricardo dos Santos were stopped by police in west London while with their baby.
The bodies of Nicole Smallman and Bibaa Henry were found in Fryent Country Park in Wembley, north-west London, in June.
Met Police boss describes the footage as “deeply disturbing” and said some of the techniques caused him “great concern”.
The force's commander said he was "horrified and disgusted" by the allegations.
The Independent Office for Police Conduct (IOPC) investigation covers six separate incidents in the Birmingham area since February.