A privately run immigration lockup in Tacoma hired security guards without required preliminary background checks and then lied about it, according to authorities.

Sylvia Wong, a human relations specialist with GEO Group Inc., the private contractor that runs the Northwest Detention Center, was charged in U.S. District Court on Tuesday with lying to federal investigators when she claimed in April she did not falsely generate documents.

“Clearly this is a cause for concern,” said Virginia Kice, a spokeswoman for U.S. Immigration and Customs Enforcement. “We take great pride in the safety and the security at our facilities, and we need to make sure the people responsible for the safety and security of our facilities are themselves beyond reproach.”

The Northwest Detention Center opened in 2004 and holds about 1,000 people accused of immigration violations, mainly detainees from Alaska, Oregon and Washington.

This summer, a report by an immigrant rights advocacy group alleged mistreatment of detainees there, including excessive strip searches and overcrowding. ICE officials dismissed it as a “work of fiction.”

Guards hired at the center are supposed to go through a preliminary background check, after which an “entry on duty” memorandum allows them to begin work pending the completion of a full background check, which can take several months to more than a year, Kice said.

Wong is accused of fabricating the documents, allowing guards to begin work without the preliminary background check. Kice said she couldn’t discuss why that allegedly was done, how long it might have been going on or in how many instances guards began working without background checks.

“If someone was brought on board who had a prior criminal history ... that’s one of the issues we’re examining closely,” she said, adding that in such a case “we’ll take follow up action.”

Wong is still on the job, Assistant U.S. Attorney Nicholas Brown said.

Wong’s lawyer was out of the office Tuesday, and Wong did not return a message left on her work voice mail. GEO Group, based in Boca Renton, Fla., did not return e-mails seeking comment.

The study on conditions at the lockup was released by Seattle-based OneAmerica, an immigrant rights advocacy group, and the International Human Rights Clinic at Seattle University Law School. They based it largely on interviews with detainees, family members and immigration lawyers.

“This really just points to what we had in our report, that there’s no oversight over these detention centers, and contractors can get away with all kinds of things,” Pramila Jayapal, executive director of OneAmerica, said Tuesday.