Hundreds of immigrant children lingered in federal detention beyond a court-mandated limit, including some who were held more than five months, according to court filings that alarmed legal advocates who say the government is failing to safeguard children.

Attorneys for detainees highlighted the government’s own admissions to longer custody times for immigrant children, contaminated food, a lack of access to medical care or sufficient legal counsel reported by families and monitors at federal facilities, as well as a renewed reliance on hotels for detention.

The attorneys’ reports were filed late Monday in a civil lawsuit launched in 1985 that led to the creation in 1997 of court-ordered supervision of standards and eventually established a 20-day limit in custody…