People in US Immigration and Customs Enforcement (ICE) custody in Northern California will no longer get mustard, mayonnaise, or ketchup with their sack lunches, according to a newly-issued federal solicitation reviewed by Quartz.

The “no mayo” policy will impact about 400 meals per week for people detained at the ICE field office in Bakersfield. Whether the change will extend to other facilities is not clear, and the reasoning behind the decision is unknown. ICE did not respond to multiple requests for comment.

The ICE solicitation says each “snack meal” shall contain:

Three slices of white or 100% whole wheat bread.

Two slices of meat (turkey or chicken).

2- to 4-ounces of vegetables, cleaned and ready to eat (carrots, celery etc.).

One individual-sized prepackaged granola bar (or similar).

A bottle of water, “16.9 fluid ounces, in plastic container,” will be provided to each detainee. Vegetarian, halal, and/or kosher meals are to be prepared upon request. By its own admission, ICE officials have had difficulty finding food suppliers in the Bakersfield area that are willing to work with the controversial agency.

Immigration on the southern US border has been marked in recent years by an increase in individuals and families with children seeking asylum. They are mostly fleeing violence and other harsh conditions in Central America. The Trump administration’s “zero tolerance” policy has left tens of thousands of asylum seekers languishing in federal custody, stretching immigration processing and detention centers beyond their limit. Some are reportedly operating at triple and quadruple capacity, and federal officials say the structures were not designed for this level of use.

What’s the point?

“Packaged meals shall not contain any glass or metal containers,” the new ICE solicitation instructs potential bidders.

Since glass and metal can be used as weapons, the proscription against them is presumably for security reasons. Similarly, ICE takes detainees’ shoelaces away during the intake process so they can’t commit suicide while in custody.

But why mustard and mayonnaise?

It could simply be a cost-saving measure. The cut follows a recent—and far more serious—announcement by the Trump administration that the government would no longer pay for education, recreational activities, or legal assistance for children in immigration detention.

Andrew Fishkin, a Bakersfield immigration attorney, however, said he thinks there could be other motives at play. Fishkin is himself a former ICE agent. He was so disturbed by what he saw on the job that he quit in 2005 to become a lawyer specializing in deportation defense.

“In this administration, I always assume a cruelty motive,” Fishkin told Quartz.

Win Eaton, an immigration attorney who also practices in Bakersfield and has represented numerous people in ICE custody, identifies as a Conservative and once chaired the county’s Republican party. However, he said he doesn’t approve of the things he sees happening today.

“I’m repulsed by what this administration is doing to people,” Eaton told Quartz. “My heart is aching from the human suffering being caused. I am deeply, deeply concerned about where we are going in this country, and I do truly believe the United States is going to be paying a heavy price for this for a very long time.”

Read the full text of the ICE solicitation here: