An order had been issued "to rescue those kidnapped, alive of course," he said at his daily news conference.
The abductees worked at a nearby prison and the incident appeared to be connected to a dispute between criminal groups, Lopez Obrador added.
The state security agency updated the number of employees kidnapped to 16, from 14 previously.
More than 1,000 members of the state and federal security forces were involved in the search operation, including a specialized team from the capital Mexico City, it said.
Relatives gathered outside the local police headquarters, hugging and crying as they waited for news of their loved ones.
"We don't want anything to happen to our brother. Please, governor, please do something for these people," said Martha Elena Rincon, the sister of one of those kidnapped.
"These are innocent, working people. They have nothing to do with any of this," added Dina Luz Rincon, another relative.
The abduction occurred on a stretch of highway that connects the town of Ocozocoautla and the state capital Tuxtla Gutierrez, some 700 kilometers (435 miles) southwest of Mexico City.
Two suspects were detained in the vicinity of the kidnapping, the state security agency said, without identifying them.
Local media released a video purportedly showing the captive workers, one of whom says that the abductors are demanding the resignation or dismissal of three state security officials.
In others videos posted online, several individuals with long guns and bulletproof vests were seen next to at least three trucks blocking a highway.
The perpetrators freed 17 women traveling in the same bus, but forced the men onboard to get out of the vehicle and took them captive, authorities said.
Confrontations between criminals and law enforcement have multiplied recently in the area, which is a transit zone for migrants and drug trafficking.
Mexico has registered more than 350,000 murders and some 110,000 disappearances -- most attributed to criminal groups -- since the launch of a controversial military anti-drug offensive in 2006.
