Retired Brig. Gen. Adeeb al-Alam had worked in the Lebanese Interior Ministry on security affairs.
Authorities had charged Alam with collaborating with the Israeli secret service, the Mossad.
Lebanese security officials said they had monitored Alam's activities for more than three months prior to his arrest Saturday, Lebanon's Naharnet news service reports, citing Arabic-language outlets.
Alam denied allegations he had worked with the Israelis to coordinate assassinations and bombing attacks on Lebanon.
His wife came forward with information he had initially withheld, though the nature of that information was unclear.
Alam said he served as a information collector for the Mossad. Several mid-ranking Lebanese officials were detained in recent months on suspicion of working with the Israelis to monitor the activity of the Lebanese Hezbollah.