A coroner's report says a woman who died in a Los Angeles police patrol car after a violent arrest by officers had cocaine in her system when she went into cardiac arrest.
The report released Monday, however, said it was unclear how Alesia Thomas died because it is difficult to know how the struggle was related.
Police officials have said an officer kicked her in the genitals.
Police Commander Andrew Smith said the investigation is ongoing.
The 35-year-old Thomas died July 22 after leaving her 3-year-old and 12-year-old children at a police station about 2 a.m.
Police said she dropped off the children because she was a drug addict who could not care for them.
Officers tracked Thomas to arrest her on suspicion of child endangerment.