A statement from the Philadelphia station confirmed Mendte is being investigated by the U.S. Attorney's Office but noted that his termination "was based on an independent investigation conducted by CBS."
Station spokeswoman Joanne Calabria said Monday that she could not elaborate on what the investigation found.
Mendte has been off the air since May 29, the day his home was searched and his computer seized as part of a probe into a possible breach of Lane's personal e-mail account, lawyers for both have said. Lane began to suspect this year that her e-mail was being accessed and forwarded to news outlets that have covered her career and social life.
Mendte's lawyer, Michael A. Schwartz, said his client would continue to cooperate with authorities.
"We look forward to a prompt resolution of their investigation," Schwartz said Monday. "We also fully expect that Larry will resume his broadcasting career."
Schwartz would not say whether he thought Mendte's career would resume at KYW-TV or another station.
Mendte and Lane anchored the 6 p.m. and 11 p.m. newscasts from September 2003 until Lane was fired in January shortly after being arrested following a confrontation with police in New York. It was the latest in a series of embarrassing off-camera incidents for Lane.
Lane's lawsuit, which was filed Thursday, also alleged that the station maliciously damaged her reputation. The station has said Lane's allegations are not true and that it will defend itself vigorously in court.
Mendte, 51, who is married to local Fox news anchor Dawn Stensland, joined the station in July 2003 after several years at the local NBC affiliate. He previously co-hosted "Access Hollywood" and worked at Chicago's WBBM-TV, KFMB-TV in San Diego and WABC-TV in New York, according to his station biography.
A message left for Lane's lawyer, Paul Rosen, was not immediately returned.
