Dozens of people who were kidnapped in the Peruvian mountains have been released less than 36 hours after they were snatched.
Armed gunmen raided the camp in the early hours of Monday
Peruvian President Alejandro Toledo said all 71 hostages were "healthy and safe" and, the government added, no ransom was paid.
Mr Toledo said the kidnappers fled when Peruvian security forces approached, and hundreds of soldiers and police were now searching for them in the remote Andean region.
For the first time, the president blamed what he termed the remnants of the Shining Path rebel movement for the kidnapping, which took place near Toccate, about 350 kilometres (220 miles) south-east of the capital Lima.
Most of the hostages worked for Argentine firm Techint, and were living in a camp while building a natural gas pipeline in the area. They all returned there on Tuesday.
The president praised the army and police, saying that the hostages were freed without paying the kidnappers - who had demanded $1m, medicines and communications equipment.
"This has been a nightmare with a happy ending," he said.
One of the freed hostages, Julio Aguilar, told local radio he believed Techint had met the kidnappers' requests.
In Lima, Techint spokesman John Hartley denied that the company had negotiated with the kidnappers.
Speaking on national television, Mr Toledo said his administration would not negotiate with guerrillas. He said the group would be beaten, and beaten within the law.
Despite a threat by the hostage-takers to kill their prisoners in the event of an assault, the president ordered about 300 army and police commandos into the region,
The hostages included three police officers, six Colombian nationals and a Chilean, the president said.
Peruvian Defence Minister Aurelio Loret de Mola said 62 "terrorists" had taken part in the abduction, of whom only 18 were actual "combatants".
The police officers taken captive had been delivering explosives to the camp, which were also stolen by the gunmen.
Peru's Foreign Minister Alan Wagner said the kidnappers may have disguised their true identity by wearing the uniforms worn by Techint workers.
The communist Shining Path group was once Latin America's most feared guerrilla group.
In the 1980s it was blamed for sparking off a two-decade civil conflict in Peru which led to the deaths and disappearances of more than 30,000 people in car bombings, assassinations and peasant massacres.
The Shining Path was dealt a severe blow in 1992 when its leader Abimael Guzman was arrested and sentenced to life imprisonment.
Guzman faces a retrial between September and November after the high court ruled that the 1992 verdict was unconstitutional.