Mayor Jim Kenney’s administration has a message for construction firms that continue to work on nonessential projects during the coronavirus pandemic:

Stop building. Or pay the price.

In a letter sent Wednesday to Philadelphia’s approximately 6,000 registered contractors, the Department of Licenses and Inspections warned that they could face stop-work orders and $1,000-a-day fines, and lose their licenses if they continue to flout city and state orders to halt most construction to slow the spread of the virus.

“Nonessential construction includes all construction EXCEPT for the construction of health-care facilities or emergency repairs specifically approved by the City of Philadelphia,” Will Fernandez, L&I’s director of audits and investigations, wrote in the letter. “Unless you have received a waiver that specifically addresses the job site at which you wish to work (not your company generally) you are otherwise not permitted to continue work and must immediately stop all work beyond what is necessary to make the building safe and secure.”

The warning followed an Inquirer report last week that Gilbane Building Co., an international development company, was continuing to work at the site of the $700 million Live! Hotel & Casino in South Philadelphia, one of the most expensive projects in the city.

The firm initially claimed it had obtained a waiver to keep building, but officials at the state Department of Community and Economic Development later said Gilbane’s waiver applied to other projects — not the casino. On April 10, L&I issued a stop-work order for the project. The sheet metal workers had left earlier in the week due to what union leaders said was a lack of coronavirus-related precautions.

Gilbane has refused to publicly disclose the number of COVID-19 cases there, but internal communications obtained by The Inquirer show that at least three workers at the casino site had tested positive. The project drew hundreds of workers, some traveling from as far away as New York and Maryland.

Karen Guss, an L&I spokesperson, said Thursday that the casino project was a “significant example of the problem” of contractors continuing to build without authorization. She said L&I has had the same concern at other sites as well.

Fernandez, in his letter, told contractors to “not give yourself the benefit of the doubt and continue working at any job sites unless you have a waiver that expressly applies to that job site.” If unsure, they should contact their local L&I construction district for guidance.

Statewide, officials have received 42,380 requests from Pennsylvania businesses for exemptions to the shutdown order. Staffers are still working through the applications. As of late last week, 7,596 had been approved, 17,010 had been denied, and 14,171 were submitted for activities for which no exemption was required, according to a state spokesperson. There are approximately one million businesses in Pennsylvania.

Companies still operating are required to take measures to protect employees, including practicing social distancing, requiring them to wear masks, and staggering start times, according to an order signed Wednesday by Pennsylvania Secretary of Health Rachel Levine. The order also sets procedures for handling positive cases of the virus.

Angela Couloumbis of Spotlight PA contributed to this article.