Minneapolis police officers asked emergency medical workers dozens of times over three years to inject suspects and others with the powerful anesthetic ketamine, including some who were already restrained, The Star Tribune reported on Friday.

In some cases, the drug caused heart or breathing failure and required those injected to be revived or intubated, according to the newspaper.

The Star Tribune said it had obtained a draft report of an investigation by the Office of Police Conduct Review, a division of the city’s Department of Civil Rights.

Ketamine has for decades been used as an anesthetic for humans and animals as well as abused as a recreational hallucinogenic drug known as Special K. Researchers have also explored its therapeutic uses in treating depression.