By Patrick Markey
BOGOTA (Reuters) - Colombian troops on Tuesday forced rebels to free all but one of 23 oil contractors working for Canada's Talisman Energy after they were snatched a day earlier in a rare mass kidnapping, authorities said.
Troops and helicopters were still pursuing the kidnappers in the remote eastern jungle region to free the last of the hostages, who were forced to leave their camp in Vichada province in the country's oil-rich east.
"We can confirm that 22 of the 23 are now freed," Defense Minister Rodrigo Rivera said. "Only one remains in their hands in an area we hope to reach soon."
Latin America's No. 4 oil producer, 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 grip.
The freed local contractors, still dressed in orange coveralls and helmets, said three people had forced them into the jungle at gunpoint. One said military pressure and explosions forced the rebels to abandon them, while another said one captor simply released them early in the morning.
"They felt the pressure because they knew well that we were going to cut them off," Armed Forces commander Admiral Edgar Cely told local radio.
Kidnappings are now rarer, but companies in Colombia are still targeted for extortion and violence by armed groups. FARC rebels kidnapped five oil contractors last year, but troops rescued them four days later.
Talisman said most of the workers were members of local indigenous communities hired by a contractor to carry out seismic work in the area.
Once branded a failing state caught up in drug and rebel violence, Colombia has enjoyed a sharp decline in bombings, kidnappings and attacks since 2002 when the government began a U.S.-backed security crackdown.
Aided by billions in U.S. funds, Colombia troops now have better intelligence and the mobility to strike at FARC camps hidden deep in jungles. But rebels and illegal armed militias linked to the cocaine trade still operate in remote areas.
The rebels last month freed six hostage troops and local politicians as a humanitarian gesture. But they are still holding around 15 police and soldiers in secret camps for political leverage.
Colombia's oil infrastructure has also been hit 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.
Foreign direct investment in Colombia has expanded more than five-fold to around $10 billion as violence has waned and oil and mine companies have moved into areas once considered off limits for exploration.
(Additional reporting by Nelson Bocanegra and Luis Jaime Acosta; Editing by Vicki Allen and Todd Eastham)