SAN ANTONIO (CN) — The city of San Antonio claims in a federal lawsuit against the Department of Homeland Security that government officials helped the Texas attorney general build his case against the city over a sanctuary ban but stonewalled requests for evidence and testimony.

“The Department has arbitrarily denied San Antonio access to its information and employees,” the 39-page lawsuit states. “The requested information is critical to San Antonio’s defense in the Underlying Lawsuit and is available only from the Department.”

In November 2018, Texas Attorney General Ken Paxton, a Republican, launched a lawsuit against San Antonio in Travis County court, seeking millions in fines for the San Antonio Police Department’s alleged interference with federal authorities’ attempts to enforce immigration law.

Paxton’s suit centered on an August 2017 incident in which 10 immigrants died after they were trapped inside a Floridian’s tractor-trailer, which was parked at a San Antonio Walmart parking lot in the summer of 2017. According to Paxton, Police Chief William McManus “personally called an immigration attorney from an advocacy organization” who said to immigrants on the scene, “Su oficina no trabaja con migración” — allegedly assuring them that SAPD does not work with immigration officials.

SAPD’s stated policy is to only refer San Antonians to Immigration and Customs Enforcement, a Homeland Security agency, if a federal deportation warrant is out for their arrest. But Paxton accuses San Antonio of failing to check the immigrants’ criminal history, which could have turned up such warrants.

In its lawsuit filed Friday in San Antonio federal court, the city asked the court to stop the Department of Homeland Security from interfering with the city’s attempts to depose federal officials who were at the scene, namely since-retired Homeland Security Investigations Special Agent Brian Johnson, and those familiar with SAPD’s communication with federal officials, particularly Special Agent in Charge Shane Folden.

San Antonio alleges Homeland Security and ICE gave Paxton and his office access to documents as well as testimony by Johnson and other relevant officials, but denied the city’s requests for the same, in violation of the Administrative Procedures Act.

In its final judgment on San Antonio’s requests, the Department of Homeland Security told the city that complying with the requests would waste its “time and resources for private purposes, rather than the conduct of agency business,” and that deposition “would be unduly burdensome.”

San Antonio argues that because the underlying lawsuit over Texas’ sanctuary city ban is between the state and the city, it “implicates issues of public interest core to the primary mission of the department.” The city says its requests were not burdensome, as it only sought a 2.5-hour deposition at a location convenient to Homeland Security and offered to reimburse the department’s expenses.

“The department already inserted itself into the underlying litigation by cooperating with and providing information to the Texas AG,” the complaint states.

Throughout the lawsuit, the city repeatedly denies being a sanctuary city and says it does not limit federal officials’ ability to enforce immigration law. The city avers that Folden and other Homeland Security officials regularly confer with SAPD officials to enforce federal law.

Paxton sued San Antonio under Senate Bill 4, the sanctuary city ban that was passed by state lawmakers in May 2017.

The law was swiftly challenged by Austin, San Antonio and El Paso County in federal court. Those cases were consolidated and heard in San Antonio before Chief U.S. District Judge Orlando Garcia, a Bill Clinton appointee who blocked the majority of the bill.

Paxton then took the matter to the Fifth Circuit, which overturned Garcia’s injunction and restored nearly all provisions of the original law in March 2018. The only portion declared unconstitutional would have fined and jailed officials who “endorse” sanctuary city policies.

Friday’s lawsuit was signed by attorney William Cochran of the Austin firm Scott Douglass & McConnico. It names as defendants the Department of Homeland Security, its acting Secretary Chad Wolf and department counsel Chad Mizelle and Warren Kaufman, as well as ICE, its Deputy Director Matthew Albence and the U.S. government.

Andy Segovia, attorney for San Antonio, said in a statement that the city “is simply asking federal authorities to provide information that is critical to the city’s defense against allegations made in a lawsuit brought by the Texas attorney general.”

“The attorney general is claiming the city has not cooperated with federal authorities. That claim cannot be properly evaluated if the federal authorities do not provide information,” Segovia said.

The Department of Homeland Security, ICE and Paxton’s office did not immediately respond to a request for comment.