The feds were apparently investigating whether Jeffrey Epstein, an accused sex trafficker, was taking young girls who appeared to be 11 or 12 onto his private jet as recently as last year, new documents show.

The brief federal investigation into Epstein’s international travel, conducted by the U.S. Marshals Service, was previously undisclosed. It resulted in an air traffic controller reporting that she saw Epstein, the now-deceased financier, disembarking his private jet near the U.S. Virgin Islands with girls who appeared to be pre-teens on one occasion, and girls between 16 and 18 years old on another occasion.

Both alleged incidents occurred between June and November 2018, according to the Associated Press.

Epstein, 66, was accused of trafficking dozens of young girls for sexual abuse over the past several years, flitting between his Palm Beach and Manhattan estates and his private Caribbean island. He was arrested on sex trafficking and conspiracy charges in July, but died by suicide in his Manhattan jail cell Aug. 10 before he could face trial. He pleaded not guilty to the sex trafficking allegations before his death.

The allegations against Epstein date back more than two decades, and Epstein even once faced federal child sex abuse allegations in Florida that were subject to a rigorous investigation. However, he later took a 2008 plea deal that allowed him to plead guilty to solicitation charges, instead of more serious trafficking penalties. His lawyers argued that after that plea deal, the abuse ended. Allegations that led to Epstein’s July arrest also relate solely to incidents that occurred between 2002 and 2005.

After Epstein pleaded guilty to the Florida solicitation charges, he was also made to register as a sex offender and wasn’t supposed to have contact with children nor fly overseas without reporting it to authorities first.

That’s why the Marshal Service went back and interviewed the air-traffic controller in the U.S. Virgin Islands on July 10, days after Epstein’s arrest in New Jersey, according to the Associated Press. New allegations showed the Epstein might’ve violated terms assigned to him as a sex offender. Federal prosecutors in New York requested the Marshal Service investigate Epstein’s travel in January, to see whether he had ever failed to properly report his travels.

That inquiry led to a request for information from France, Monaco, Austria and Morocco — all countries he traveled to via his private jet — according to CNN. It became clear that Epstein failed to tell officials of two countries he visited entirely, and sometimes gave officials short notice that he was leaving the U.S., according to CNBC.

The Marshals Service also met with a Miami Herald reporter who remains unnamed in the documents. The Miami Herald published an extensive investigation into Epstein’s alleged wrongdoing in November, spurring renewed interest into the long-standing allegations against him.

The Marshals investigation, however, concluded after Epstein’s suicide in August.

Federal investigators have pledged to continue investing his co-conspirators, who sometimes organized the girls’ travel or allegedly engaged in the abuse, too.