The many construction cranes on the Boston skyline are about to screech to a halt in the name of curbing the spread of the coronavirus, by mayoral mandate.

During a Monday press conference, Mayor Marty Walsh ordered construction companies to stop work amid a growing coronavirus pandemic and out of precaution for workers’ safety and health. The top public health guideline in halting the spread of the virus is for people to socially distance and largely stay at home.

"COVID-19 is one of the greatest public health challenges our city has ever faced, and the steps that we take now to mitigate its spread are critical for the wellbeing of our residents," Walsh said in a statement. "We understand these steps are disruptive for our daily lives, and I want to remind everyone that this is a citywide effort that requires everyone to do their part to help us keep our city strong and resilient. I thank all of our residents, especially our first responders and medical staff, our educators, and everyone who is making a difference."

Regular activity at construction sites is suspended, effective Tuesday, but companies have until March 23 to wind down activity, secure sites and take measures to prevent trespassing. Skeleton crews will be allowed on project sites for the duration of the suspension, which has no definitive timeline, to keep the premises safe.

The only construction activity allowed at this time is emergency work, like utility repairs or work at public facilities, approved by the Boston Inspectional Services Department. The department will grant exceptions to the construction moratorium on a case-by-case basis if the proposed work is aimed at increasing public health and safety.

The policy “will be reviewed at regular intervals,” according to the mayor’s office.

Walsh’s order is expected to impact more than 21M SF of development, the Boston Business Journal reports. The move was expected to impact “tens of thousands” of construction workers, the mayor said Monday. The construction ban comes as cases of the coronavirus soar in Massachusetts.

There were 33 confirmed cases of the coronavirus in Boston, Walsh said Monday. The number of official cases hit 197 in Massachusetts Monday, but some estimates say the figure could actually be as high as 6,000 due to a large number of infected people not having access to testing.