(CNN) US Customs and Border Protection is investigating allegations that border agents mistreated migrant children held in Arizona, allegations that include sexual assault and retaliation for challenging conditions in border stations.

The allegations were first reported by NBC News . The accounts were included in documents that case managers for the Department of Health and Human Services prepared between April 10 and June 12.

The accounts come amid growing concern over conditions at border facilities and broaden the scope of allegations of mistreatment and unsanitary conditions in CBP facilities from Texas to the Yuma Border Patrol Sector in Arizona.

In June, a team of doctors, lawyers and advocates warned of what they described as major health and hygiene problems at facilities in Texas, prompting court-ordered inspections and nationwide protests calling for their closure.

US Customs and Border Protection said in a statement Wednesday that the new allegations in Arizona "do not align with common practice at our facilities and will be fully investigated."

The Department of Homeland Security's Office of Inspector General is already investigating the sexual assault allegation, according to the statement.

"US Customs and Border Protection treats those in our custody with dignity and respect and provides multiple avenues to report any allegations of misconduct. We take all allegations seriously and investigate all formal complaints. CBP Agents and Officers are expected to adhere to our policies and procedures, including those outlined in our National Standards on Transportation, Escort, Detention and Search," the statement said.

CNN is working to obtain the reports collected by case managers in Arizona.

According to NBC News, the reports include an account from a 15-year-old-girl from Honduras who said an officer put his hands inside her bra, pulled down her underwear and groped her "as part of what was meant to be a routine pat down in front of other immigrants and officers."

In another account, a 16-year-old Guatemalan boy said CBP agents took the mats out of their cell in retaliation for complaints from him and others about the taste of the water and food, according to NBC News.

Children who passed through the Yuma border station "reported being denied a phone call, not being offered a shower, sleeping on concrete" or falling asleep without eating before their 9 p.m. dinnertime, NBC News reported.

The accounts came from what HHS calls "significant incident reports," which include reports of verbal threats, physical altercations or allegations of sexual abuse.

HHS said it requires all care providers to report incidents affecting a child's health, well-being and safety. Care providers must submit a completed Significant Incident Report within four hours of the significant incident, or within four hours of the care provider becoming aware of the incident.

Care providers must report severe incidents to CPS, the state licensing agency and/or local law enforcement, according to HHS.

The Office of Refugee Resettlement elevates emergencies and serious incidents within its leadership to ensure children receive care and protection, and that facilities and ORR field staff get support in handling the most difficult and sensitive situations, according to HHS.