The teen — who was found early Wednesday morning in downtown Winnipeg — was in the care of Child and Family Services.
Police are saying little about the attack, except to say the victim, who was found around 5 a.m., is in critical condition.
Family Services Minister Kerri Irvin-Ross told reporters she was shaken.
"I'm saddened and outraged by this cowardly attack on a vulnerable child," she said, fighting back tears. "It is infuriating that there are people out there that would prey upon an innocent child.
Irvin-Ross added she's deeply troubled that this has happened to a ward of Child and Family Services.
"We have a responsibility to protect children in our care and provide them with places of safety."
Irvin-Ross said that by June 1, no child in care will be housed in a hotel.
She couldn't explain how the teen left the hotel or how many people might have been supervising her at the time.
The government will investigate the circumstances, but she said social workers are not able to restrain a teen who is determined to leave.
Irvin-Ross had promised in November to stop housing foster kids in hotels when 15-year-old Tina Fontaine was killed after running away from one.
"What today's tragedy does is remind us that we need to move a lot faster," she said Wednesday. "We need to set some concrete timelines."
The province is creating new emergency foster home spots and reducing its reliance on outside contract workers over two years. Hotels are a last resort, Irvin-Ross said, but the number of children in care has risen recently and there aren't enough alternatives. It takes time to build up a healthy roster of foster and group home spaces, she added.
Manitoba has around 10,000 children in care. The vast majority are aboriginal.
On any given day, dozens of those children are put up in hotel rooms because there isn't room in a foster home. There are now nine children being housed in hotels.
Manitoba was criticized by its own children’s advocate as far back as 2000 for putting children in hotels. The children’s watchdog has released several reports since then that have raised concerns about the practice.
Progressive Conservative critic Ian Wishart said the NDP government has had years to address this crisis. Hotels are the worst place to put a vulnerable child, he said.
"There is very little supervision," Wishart said.
"They are taking them from a medium-risk environment, in many cases, and putting them in the absolute highest-risk environment you can imagine."