Four protesters delayed but failed to halt the test of a British nuclear weapon Wednesday by infiltrating the remote Nevada Test Site and making their way to ground zero.

The device, with an explosive punch up to 12 times the force of the Hiroshima atomic bomb, was detonated more than two hours behind schedule after the four were removed by security officers."We're very pleased with the success of the protest," Junior Bridge, a spokeswoman for the Greenpeace organization, said after a 22-hour game of hide-and-seek with federal authorities.

"The controllers are showing signs of relief that it's over," Energy Department spokesman Jim Boyer said following detonation of the device at 11:17 a.m. PST. "They're obviously glad that it went, and went without any prolonged delays because of the infiltrators."

It was the second time in three years anti-nuclear activists have infiltrated the secret sprawling desert site to delay a nuclear test.

Motion from the blast was felt at Las Vegas City Hall and atop the city's highrise hotels. It measured 5.1 on the Richter scale at the National Earthquake Information Center in Golden, Colo.

Energy Department officials rejected claims the four protesters were near ground zero until they popped into view of cameras monitoring the blast site during a technical hold six minutes from detonation.

The four were rounded up by security guards who rushed to the scene in vehicles while a helicopter hovered overhead.

They were taken to Mercury, Nev. and were expected to be turned over to Nye County authorities. They would likely face trespassing charges, Boyer said.