The four, working for the Bonatti construction company, were near a complex of Italian oil giant ENI in the region of Mellitah when they were nabbed on Monday, the Italian foreign ministry said.
"A large number of security forces are trying to determine where the Italians are, carrying out searches close to where they were kidnapped," the Libyan official said.
"Up until now we have not made any progress (in finding them), and no arrests have been made."
Plunged into chaos after the 2011 overthrow of dictator Moamer Kadhafi, Libya has two parliaments and governments vying for power, as a slew of armed groups battle for control of its oil wealth.
Italy closed its embassy in Libya in February and had urged its citizens to leave the country over the escalating violence.