Construction of Hamilton's first outdoor shelter — including 40 tiny homes to house about 80 people this winter — has been halted by Ontario's Ministry of Labour.

The city was issued an order to comply last week by the ministry. The province received a complaint about how work was being carried out at the Barton-Tiffany lands in central Hamilton, according to a Nov. 22 staff communication update to councillors and the mayor.

The order requires the city to register the project with the ministry, hire a general contractor, compile a list of "designated substances" that workers could be exposed to on the job, and appoint a supervisor, the last of which the city has been done, the staff update said.

"The city has taken immediate action to comply with the ministry's order," said the update.

But in the meantime, "all work on site has been paused" while staff "work expeditiously" to be in compliance with provincial legislation.

The city told CBC Hamilton it's aiming to open the shelter by Dec. 20.

Council approved the outdoor shelter in September to provide temporary housing to people experiencing homelessness by December. It will cost about $7 million to set up and provide supports and services there for a year.

Mayor Andrea Horwath pushed for the initiative to roll out quickly, hoping it would reduce the number of tents in parks and accommodate couples and people with pets who are less likely to find indoor shelter space.

Before the work was stopped, the city had been preparing the otherwise vacant and contaminated land, including installing fence posts, hiring security guards and completing a site plan, the update said. Next steps include finishing the fence and laying asphalt to act as a barrier for contaminated soil before setting up the tiny homes and shared amenities.

The ministry's order said an inspector visited the property at 259 Caroline St. on Nov. 19 and met with the city's housing director, two corporate security managers and two foremen installing the fence.

The project was about one per cent complete, noted the order, posted to the city's website.

The visit was prompted by a complaint about the city not creating a list of designated substances before beginning construction, the order said.

Designated substances are chemicals or biological agents hazardous to worker health. They include mercury, lead and arsenic.

While the city had conducted an environmental examination of the site, it hadn't prepared a list to distribute before seeking contractors to bid on the project, the ministry's order said.

It also found the city hadn't registered the project with the ministry before starting. It's required to do so for all projects valued over $50,000, the order said. The deadline to comply is Dec. 23.