Federal law-enforcement authorities in New York are investigating whether Uber Technologies Inc. used software to interfere illegally with a competitor, according to people familiar with the investigation, adding to legal pressures facing the ride-hailing company and its new chief executive.

The investigation, led by the Federal Bureau of Investigation’s New York office and the U.S. attorney’s office in Manhattan, is focused on a defunct Uber program, known internally as “Hell,” that could track drivers working for rival service Lyft Inc., the people said.

“We are cooperating with the SDNY investigation,” said an Uber spokesman, referring to prosecutors in the Southern District of New York. He declined to offer additional details.

Uber hasn’t publicly discussed the details of the program.

People familiar with the matter said “Hell” worked like this: Uber created fake Lyft customer accounts, tricking Lyft’s system into believing prospective customers were seeking rides in various locations around a city. That allowed Uber to see which Lyft drivers were nearby and what prices they were offering for various routes, similar to how such information appears when an authentic Lyft app is opened on a user’s smartphone, these people said.