A Lebanese army colonel and a senior retired customs officer have been detained on suspicion of spying for Israel, Lebanese security sources said on Sunday.
The army officer is the second colonel arrested in less than a week in an espionage investigation that has produced charges against at least 21 suspects and several confessions, Lebanese authorities say. Israel has not commented on the arrests.
Investigators have displayed what they say is spy gadgetry seized in the course of the investigation. Some suspects were also found carrying forged passports, computers, cameras and scanners used for storing information on sensitive locations.
At least two spies fled to Israel last week, Lebanese authorities have said, demanding their repatriation.
Senior Lebanese security officials say the arrests have dealt a major blow to Israel's spying networks in Lebanon.
They say many of the suspects played key roles in identifying Hezbollah targets that were bombed during the 34-day war between the militant group and Israel in 2006.
Other suspects have been charged with monitoring senior Hezbollah officials and at least one is alleged to have played a role in the 2004 assassination of a commander of the group.
Thirty-five individuals are suspected of espionage thus far, of whom 22 have been detained while most of the rest are being pursued by Lebanese authorities.
The suspects are believed to have been instructed to gather information on Hezbollah facilities and the homes of high-ranking militants.
The detained army official was named as Mansour Diab, 48. He is suspected of working for Israeli intelligence for over 10 years in return for generous compensation.
Diab is believed to have been recruited in 1997, when the Lebanese army sent him to the United States for a training course. Diab later went on a number of trips abroad, and authorities are investigating whether he was in contact with Israeli intelligence during those visits as well, and whether he had visited Israel, as other espionage suspects are believed to have done.
Other suspects detained recently include the former mayor of the Sunni village of Saadna'il in the Bekaa.
Spying for Israel is considered treason in Lebanon and is punishable by death.
Lebanese authorities said recently that the arrests were made by security services equipped and trained by the United States.
Lebanon's army released a statement this week blaming the political instability in the country on Lebanese citizens spying for Israel.
"The unstable political atmosphere has created a comfortable environment for the enemy to penetrate," it said. "Some people weak of character were recruited by material or sexual temptations."