Outraged British diplomats are still demanding an explanation for the "outrageous" detention, which began when dozens of police surrounded the "Hubco" power plant, 24 miles from Karachi, on Friday.
It is thought that the expatriate workers fell victim to a legal battle between a Pakistani firm Hub Power Co Ltd (Hubco), which runs the power station, and the government, over electricity tariffs.
Prime Minister Nawaz Sharif's government has been feuding with 21 privately run power companies, accusing them of overcharging for electricity after paying bribes to the former prime minister Benazir Bhutto when she was in power.
The Britons, who with their partners live and work at the plant, were told they would be arrested if they tried to leave. "We are obviously relieved that a rather unpleasant situation has ended," said Dan Cowell, a security manager.
Jayd Davies, press attache for the British High Commission in Islamabad, said: "This was a deplorable action. Putting restrictions on British nationals is an outrageous action." He complained that "there has been no official explanation from the relevant authorities so far". Mr Davies said the High Commission in Islamabad was making representations to government ministers.
The trouble started on Tuesday, when police chiefs from the nearby town of Hubchowki visited the site and informed the managers that British nationals could not leave without prior permission.
At same time, armed police were stationed outside the compound gates and began checking vehicles and people entering and leaving the power plant.
On Friday, local police said the instructions had been changed, and any Briton who tried to leave the complex would be arrested. The same day, police stopped supplies of food and water being taken into the complex. The police who surrounded the site claimed they were acting on orders from "the very highest level." The blockade was lifted about midday yesterday, following protests from British officials in London and Pakistan.
n Islamabad (AP) - Five men hijacked a Pakistan International Airlines plane with 38 people aboard yesterday, demanding to go to India, but a Pakistan air force fighter jet intercepted the plane and forced it to land in Pakistan. The hijackers were reported to be tribesmen from Baluchistan province, protesting against Pakistan's plans to conduct a nuclear test in the area.Reuse content