WASHINGTON—Chinese corporate espionage has metastasized into a critical national and economic security threat, top federal investigative officials told U.S. senators on Wednesday, issuing stark warnings that Beijing is exploiting American technology to develop its own economy.

The disclosures, at a Senate Judiciary Committee hearing, came as the Trump administration is preparing to lay out an unprecedented amount of evidence in coming days about Chinese spying and hacking operations designed to steal secrets from U.S. companies.

“Our prosperity and place in the world are at risk,” said Bill Priestap, the FBI’s top counterintelligence official. He later disclosed that the bureau has received thousands of complaints about suspicious activity by alleged Chinese government spies at research institutions in the U.S., and that every FBI investigation in these areas has unearthed larger problems.

“I believe this is the most severe counterintelligence threat facing our country today,” Mr. Priestap said. “Every rock we turn over, every time we looked for it, it’s not only there, it’s worse than we anticipated.”

Officials from the FBI, Justice Department and Department of Homeland Security testified before the Senate panel, with federal prosecutors poised to unseal criminal charges shortly against hackers linked to the Chinese government.