Tests show that a coyote found dead in San Francisco's Douglass Playground last month died of massive internal bleeding as a result of eating rats that had been poisoned, according to the state Department of Fish and Wildlife.

Urban coyote deaths are usually caused by injuries associated with car crashes, but X-rays showed that was not the case this time. The carcass found at the park near Douglass and 26th streets in Noe Valley tested positive for four different kinds of rat poison that are not legal for non-professional use in California.

Officials believe the coyote must have ingested the poisons from at least four different sources. It's not possible to pin down exactly how that happened, but it's believed to be a result of either residents or businesses hiring commercial pest control operators or the illegal use of restricted rodenticides.

Most anti-coagulant rodenticides have been restricted to use by pest care professionals under regulations enacted in 2014, according to the San Rafael-based wildlife advocacy organization WildCare.

Homeowners and residents are being urged to properly dispose of any previously purchased products that contain brodifacoum, bromadiolone, difethialone or difenacoum.

Rodenticides are not used in city parks, including Douglass Playground, according to state wildlife officials, and San Francisco maintains a strong anti-rodenticide stance.

Information from WildCare about alternative pest control methods is available at www.wildcarebayarea.org/rodenticide.