In early February, Mariano Pena Lezama leased a pink warehouse in San Francisco’s Bayview industrial district to house his janitorial company. He said he planned to use the space to park his trucks and store cleaning supplies, according to the warehouse owners’ attorney.

But within days, the building at 2266 Shafter Ave. was allegedly converted into an unlicensed after-hours nightclub for mass gatherings of drinking, dancing and gambling, creating one of the region’s more brazen examples of people disregarding shelter-in-place orders during the coronavirus outbreak.

“There was a party every night,” Monte Travis, an attorney for the building’s landlords, told The Chronicle on Monday.

In the weeks since San Francisco’s March 16 shelter-in-place order, the parties became more raucous and frequent, according to workers at neighboring businesses. Investigators said more than 100 people were seen attending parties, often while ignoring physical distancing requirements.

Lezama leased the property for his business, Bay Area Pinnacle Cleaning, but he instead turned it over to illicit club operators, according to court documents. The tenant previously ignored a three-day eviction order, prompting San Francisco police and the city attorney’s office on Saturday to shut down the underground club for violating public health orders designed to slow the spread of COVID-19.

Lezama could not be reached for comment.

City Attorney Dennis Herrera said the landlords — family members Andrew Trinh, May Lee, Nam Trinh and Trang Thai — cooperated with the investigation and the police shutdown.

The raid was conducted with an abatement warrant Herrera obtained Friday, allowing the police to station cars in front of the warehouse that night in an effort to deter people from entering. Police raided the warehouse hours after it closed Saturday, seizing everything from cases of beer to gambling machines and DJ equipment.

In the eviction complaint, Travis said the warehouse was used “to operate an illegal unpermitted gathering of 100-plus persons that began after midnight, peaked in the hours between 2 and 6 a.m. and generally continued until dawn or later.”

No one has been arrested in connection with the nightclub and Herrera’s office did not issue citations or fines.

“The most important thing was for us to shut down the establishment and make sure it was no longer in operation,” Herrera said in a video call with reporters Monday. “Could there be other civil actions? We’ll see.”

San Francisco police declined to discuss the nightclub and any possible arrests or citations, saying the matter remains under investigation. Authorities also declined to release a report of a similar incident at the warehouse April 6.

Herrera declined to discuss whether any other clandestine clubs or speakeasies are operating in the city, but he said his office will consider any complaint about a business or activity violating the shelter-in-place orders and determine whether it requires action.

Owners of the property were not only upset with being duped, Travis said, but they also feared their building — with a single entrance and no sprinklers — could become a fire hazard like the Ghost Ship warehouse in Oakland, which caught fire Dec. 2, 2016, and killed 36 people attending an electronic music concert.

Travis said “the shelter in place took effect and the parties just continued with flagrant disregard for safety — of not just themselves but everyone else in the city and the Bay Area.”

Michael Cabanatuan is a San Francisco Chronicle staff writer. Email: mcabanatuan@sfchronicle.com Twitter: @ctuan