SAN ANTONIO (AP) — One person was in federal custody Friday as an investigation continued into a mysterious 911 human trafficking call in Texas, federal officials said.

No other information could be provided, according to a U.S. Immigration and Customs Enforcement statement. A message to the U.S. Attorney’s Office in San Antonio seeking more details was not immediately returned Friday.

Federal, state and local authorities in Texas have been searching for a tanker truck days after a 911 caller in the San Antonio area reported dozens of people were trapped inside it. The caller said Monday that there were an estimated 80 people inside the truck’s tank — typically used to haul liquids or gases that can be hazardous — and that they couldn’t breathe.

“The investigation is still ongoing as agents are following up on leads to further the case and ensure the safety of the individuals,” the ICE statement said.