Immigration advocates and health care workers on Wednesday slammed U.S. Immigration and Customs Enforcement for requesting tens of thousands of N95 masks for its agents as hospitals across the U.S. face a dire shortage of the protective masks to treat COVID-19 patients.

ICE said it needs 45,000 N95 masks for 26 of its field offices that handle “enforcement and removal operations” in a proposal posted to a government bidding website Friday. Agency officials said they “would like delivery within 30 days,” even though the masks have been deemed critical for health professionals who treat patients infected with coronavirus. The masks are thicker than regular surgical masks and are designed to block out airborne particles and liquid.

Health care workers in the Bay Area and around the world have made desperate pleas for more masks, which are among the only personal protective equipment, or PPE, that can shield them from the virus. Many doctors and nurses have reported reusing masks several times, though the U.S. Food and Drug Administration says they should not be shared or used more than once.

As of Wednesday afternoon, the U.S. had more than 55,500 cases of coronavirus and more than 800 deaths, including more than 60 in California. More than 451,000 people have tested positive worldwide, and more than 20,400 have died.

An ICE spokeswoman on Wednesday said the masks are part of “standard law enforcement personal protective equipment,” but she declined to answer questions about why the agency needs 45,000 masks and who would use them. It is unclear whether undocumented immigrants who are arrested or detained would receive masks.

The agency said it has more than 20,000 law enforcement and support personnel in more than 400 offices in the U.S. and around the world, but officials did not say how many employees work out of the 26 Enforcement and Removal offices. The division within ICE oversees the transport, detention and deportation of undocumented immigrants.

Amber Akemi Piatt, director of the Health Instead of Punishment program at Human Impact Partners, a social justice organization in Oakland, slammed ICE’s request for the masks.

“It’s deeply cynical, it’s disgraceful, and it’s not surprising,” she said. “ICE has long been an agency with a record of systemic abuses and no real consideration for the health and safety of our community members.”

Brian Grady, a physician and president of the San Francisco-Marin Medical Society, said the request “flies in the face of all the public health measures to combat and minimize the spread of COVID-19.”

“We are currently experiencing a severe shortage of PPE, particularly N95 masks, for health care workers,” he said in a statement. “Requisitioning a large number of these to further the effort to arrest and detain people sends exactly the wrong message at this time.”

Doctors, nurses and medical staff have posted videos online calling for mask donations, and many businesses and organizations have stepped in to try to fill the growing demand. Volunteers across the U.S. have started sewing their own masks and donating them to hospitals, and Apple CEO Tim Cook on Wednesday said the Cupertino company will donate 10 million masks to the U.S. and “millions more” for the regions in Europe most affected by the pandemic.

Facebook, which is based in Palo Alto, said it plans to donate 720,000 masks — a combination of the coveted N95 respirators and more basic surgical masks — and 1.5 million pairs of gloves to health care workers around the world. Facebook officials said they bought the masks for their offices’ emergency disaster kits following wildfires in California in recent years.

Flexport, a San Francisco company that uses software to make international trade more efficient, donated 60,000 surgical masks, 34,000 gloves, 2,000 surgical gowns and 50 thermometers to health care workers across the city last week.

Tatiana Sanchez is a San Francisco Chronicle staff writer. Email: Tatiana.sanchez@sfchronicle.com Twitter: @TatianaYSanchez.