MELBOURNE, Australia — The driver of an S.U.V. who plowed into a crowd on a busy Melbourne street on Thursday, injuring 19 people, was mentally ill, Australian officials said, describing the attack as a deliberate “act of evil” but not terrorism.

“This is a terrible, evil, cowardly act and one that will be condemned by all Victorians,” Daniel Andrews, the premier of the state of Victoria, said at a news conference, hours after the perpetrator drove a white Suzuki S.U.V. through a busy intersection in central Melbourne.

“We haven’t yet identified any linkages between him, extremism, any extremist groups or anything to do with terrorism at this time,” Shane Patton, Victoria’s acting police commissioner, told reporters on Friday. He said investigators had conducted a “preliminary conversation” with the suspect.

“During that conversation,” Mr. Patton said, “he made what I can best describe as utterances in respect to a range of things about hearing voices, about dreams, but also attributing his actions to perceived mistreatment of Muslims. Obviously we need to explore all of that.”