Colombian troops have freed all but one of the 23 local oil contractors who were kidnapped yesterday by suspected Farc rebels.
The hostages were working for Canadian operator Talisman Energy, which said most were members of local indigenous communities hired to carry out seismic work in the area.
Troops on foot and in helicopters were pursuing the kidnappers in the remote eastern jungle region to free the remaining hostage, the minister of defence said.
"We can confirm that 22 of the 23 are now freed," Rodrigo Rivera told local Caracol Radio.
The government had earlier said 19 of the workers had been freed.
Colombia is enjoying an investment boom in petroleum and mining as violence from its long war has subsided, but illegal armed groups remain a threat in remote areas where the state has yet to gain a strong hold.
The rebels operate in Vichada province along with illegal cocaine-trafficking gangs, in the oil-rich flatlands of eastern Colombia near the Venezuelan frontier.
Kidnappings have become rarer in Colombia as security has improved, but yesterday's large-scale hostage-taking shows the risks still facing the oil and mining firms. Companies are still targeted for extortion by armed groups.
The Farc still kidnap for ransom but they are also holding about 15 police and soldiers hostage for political leverage.
The country's oil infrastructure has also been attacked recently. Last month, the Cano Limon-Covenas pipeline was attacked and earlier the Transandino oil line was halted for a few days by a suspected rebel bomb.
Last month, a coal rail line operated by the coal producer Cerrejon was also hit by a bomb in a second attack on the installation in a month.
Once written off as a failing state mired in drug violence, Colombia has enjoyed a sharp decline in bombings, kidnappings and attacks since 2002, when the government began a U.S.-backed security crackdown on armed groups.
Foreign direct investment grew more than five-fold as violence waned and oil and mining companies moved into areas once considered off limits for exploration.
The Farc and cocaine-smuggling militias linked to former paramilitaries are still proving resilient in remote jungles, mountains and flatlands, however, where the Colombian state has yet to establish a strong foothold.
Reuters