Rancho Veal Corp., which operates the Bay Area's last major slaughterhouse in Petaluma, is recalling 41,683 pounds of meat that didn't receive a full federal inspection, the U.S. Department of Agriculture announced Monday.

No illnesses have been reported, but a USDA press release Monday called the recalled meat "unfit for human food" due to the alleged lack of a complete inspection. The issue came to light as part of an ongoing investigation that brought federal agents and Petaluma police to the plant on Petaluma Boulevard North last week.

The meat, including carcasses and boxes of beef tongue, hearts and other items, was produced Wednesday and shipped to distribution centers and retailers in California, according to the press release.

The USDA on Monday listed six retailers in the Bay Area and one near Los Angeles that received the now-recalled meats. The list was considered preliminary and possibly incomplete.

Rancho Veal's owners, Jesse "Babe" Amaral and Robert Singleton, did not respond to requests for comment left Sunday and Monday at their homes, as well as at their business Monday.

Workers were present at the plant Monday, and some cattle stood in holding pens.

The Bay Area and North Coast used to have a number of slaughterhouses. Now, with the exception of a small processing plant for sheep and goats near Occidental, Rancho Veal is the sole animal processing facility for Sonoma, Napa, Marin, Lake and Mendocino counties.

"It's a significant part of our whole Sonoma County livestock industry," said Tim Tesconi, executive director of the county's Farm Bureau.

Rancho Veal's services include slaughter for the North Bay's high-end, grass-fed beef operations. The company reportedly began processing hogs in 2012.

Over the years, Rancho Veal has been targeted by animal rights activists. Police in 2000 said arsonists set fires at the plant and at two poultry operations also in Sonoma County. That same year animal rights activists demonstrated outside Rancho Veal.

San Francisco television station KPIX 5 reported that USDA agents and Petaluma police served a search warrant at the plant Friday.

Petaluma police Lt. Tim Lyons confirmed that officers went to the plant on Friday but referred questions to the Agriculture Department. USDA representatives in Washington, D.C., directed inquiries about Friday's action to the U.S. Attorney's Office in San Francisco. A spokesman for that office declined comment.

By Monday afternoon, the agriculture agency released a press release on the voluntary recall.

"The problem was discovered as a result of an ongoing investigation," the release reported. The agency "believes the company produced product without full ante-mortem inspection as per federal regulations."

The USDA reported it has received no reports of illness connected to the recalled meat.

The seven retailers named on a distribution list for the recalled meat are: Del Monte Meat Co., American Canyon; C-M Meat Co., Berkeley; La Morenita Market, Napa; Vallerga's Market, Napa; Del Monte Meat Co., Oakland; Prime Smoked Meats, Oakland; and RBR Meats, Vernon.

Officials for four of the seven retailers were unavailable for comment Monday afternoon.

The USDA said the recalled meat carcasses and boxes can be identified by the establishment number, "EST. 527," inside the USDA mark of inspection. Each box also bears the case code number "ON9O4."

The boxes of recalled meat include:

50-lb. boxes of "Beef Feet"