Staff from the House oversight and judiciary committees visited the Texas prison where Ghislaine Maxwell, the longtime associate of Jeffrey Epstein, is serving her sentence, according to Democratic lawmakers.

In a statement, the Democratic representatives Robert Garcia and Jamie Raskin said staff from the committees traveled to the minimum-security federal prison camp in Bryan, Texas, on Tuesday to seek answers about Maxwell’s transfer there, and about allegations that she has received preferential treatment at the prison camp.

According to the Democratic lawmakers, prison staff provided the committee staff with “an extensive tour of the grounds and programming of the facility”.

However, the lawmakers claimed that the “Bureau of Prisons leadership repeatedly shut down our lines of questioning or could not provide basic information about our central concerns, including Ms Maxwell’s extraordinary treatment, allegations of sexual assault at the facility and retaliation against inmates who tried to blow the whistle.

“We also have serious concerns about the accuracy and veracity of information received by our investigative staff,” the lawmakers said, adding that their investigation would continue.

In a statement, a spokesperson for the Bureau of Prisons (BOP) said that it “facilitated an extensive and transparent visit of the facility for Congressional staffers from two committees and both sides of the aisle”.

“Each of the topics mentioned were addressed to the extent possible” they added. “BOP staff cannot provide statements about ongoing investigations, personnel actions or litigation, nor would they know the details of any active or potential investigations conducted by external or independent parties.

“The BOP went to great lengths to accommodate this visit and spent hours responding to questions from Congressional staff,” they continued.

“We acknowledge the importance of transparency and respect the role of elected officials overseeing government operations,” the statement concluded. “We remain committed to working with our Congressional partners.”

Maxwell is currently serving a 20-year prison sentence for her role in Epstein’s sex-trafficking scheme. Last summer, she was transferred from a federal prison in Florida to the minimum-security Bryan prison camp, which houses about 635 female inmates.

The move came about a week after Maxwell was interviewed by the then deputy attorney general, Todd Blanche, about the Epstein case. The interview occurred amid mounting political and public pressure on the Trump administration for more transparency around the Epstein case and to release more records related to the late convicted sex offender.

Maxwell’s transfer sparked backlash, especially from Democrats, who noted that convicted sex offenders are generally placed by the BOP in low-security prisons, such as the Florida prison where Maxwell had previously been held, rather than minimum-security facilities.

Speaking to CNN this week, Garcia said that the prison’s warden told the committee staff during the visit on Tuesday that “of the 600-plus women that are there, [Maxwell] is the only convicted sex offender at that facility, and he could not answer and does not know why she was actually moved there”.

Garcia also said that the staff were not granted access to Maxwell during the visit.

“Uniformly, by the way, all the staff came back with the same conclusion, which is that this is a park-like campus, and Ghislaine Maxwell should not be there,” he added.

Blanche has defended the transfer, arguing that it was necessary for Maxwell’s safety, citing threats against her.

The congressional visit this week follows a November letter Raskin sent to Donald Trump, in which he said that the judiciary committee had received information from a whistleblower alleging that Maxwell had been receiving favorable treatment at the Texas facility.

In the letter, Raskin asked the president whether he had directed Blanche or “anyone else in your administration to provide Ms Maxwell with the transfer to the prison camp, favorable and preferential treatment in prison, or special accommodations for her communications and interaction with her family and the outside world”, among other questions.

Among the allegations were claims that Maxwell received custom-prepared meals, that her guests were permitted to bring computers, and that she had access to a puppy and more.

At the time, the BOP said in a statement that “allegations of misconduct, including any suggestion of preferential treatment, are taken seriously and thoroughly investigated” through internal processes. It added that violations of this policy can result in disciplinary action that can include firing and prosecution.

The BOP’s standards of employee conduct “explicitly prohibits all staff from providing preferential treatment to any inmate”, the agency said.

In January, Raskin and Garcia sent another letter, this time to the then attorney general, Pam Bondi, calling on her to allow them to visit the Texas prison camp and to interview the warden.

In the letter, they said more than a dozen whistleblowers had come forward with accounts of Maxwell’s treatment and other alleged incidents at the facility.

The lawmakers said that among the allegations were claims that Maxwell had been allowed to use a laptop without supervision, that she was able to keep more personal and legal possessions than other inmates, that she was provided bottled water while other inmates drank tap water, and that she had been granted access to staff-only areas to watch television alone.

Maxwell’s lawyer, David O Markus, in January rejected the allegations that Maxwell was receiving preferential treatment.

In a statement to the New York Times, he said that “the rule of law matters most when it protects the least popular defendant”, adding: “Humane treatment isn’t special treatment, and political prison tours don’t move the country forward.”