The largest Muslim civil rights organization in the United States on Thursday urged the Department of Homeland Security to immediately restore Muslim community access to security grants following a deadly attack at a mosque in San Diego.

In the letter to DHS Secretary Markwayne Mullin, the Council on American-Islamic Relations (CAIR) warned that Muslim communities in the U.S. are being deprived of opportunities under the nonprofit security grant program to enhance their security as long as DHS fails to address reports that Muslim groups have been denied equal access to these funds.

"Unfortunately, under prior DHS leadership, American Muslim organizations across the country reported widespread concern that they were being excluded or discouraged from participating in the (grant) program,” the letter said.

It mentioned media reports saying that the DHS had paused and stripped funding from dozens of Muslim organizations using vague and reportedly bad-faith allegations of extremism.

The letter cited a pattern of anti-Muslim attacks on mosques across the country, including planned mass shootings, arson attacks, bomb threats, and violent assaults, and emphasized the importance of administering federal security programs to protect Muslim communities.

The letter came after three people, including a security guard, were fatally shot Monday at the Islamic Center of San Diego in an attack that authorities are investigating as a hate crime. Law enforcement officials said the two suspects died from self-inflicted gunshot wounds.

The attack took place the week before the Muslim holiday of Eid al-Adha and the annual Hajj pilgrimage to Mecca.