CARSON CITY, Nev. (AP) _ Three bomb ranges used by the Fallon Naval Air Station reopened Friday following a helicopter sweep to ensure that none of the camouflaged protesters who forced the ranges to shut down were still in hiding.

Base spokesman Steve Burghardt said the sweep was made after a member of the Coalition of Rural Americans, which organized the demonstration, called to say the protesters were off the ranges by late Thursday.

Burghardt also said officers at Fallon, the Navy's main West Coast bombing and flight training base, have begun ''investigating different types of actions that are available'' to prevent another bomb range shutdown.

He said options could range from possible legal action against the protesters to patrols of the bomb zones, ranging in size from about 17,000 acres to 40,000 acres.

Richard Bargen, spokesman for the Coalition of Rural Americans, said his group may send more people onto the bombing ranges. He said another move may be made in about two weeks and continue every week or two if necessary.

Bargen said the group wants an independent report on the impact of base activities on area residents, including the impact of increased sonic booms.

He said the coalition wants the Navy to ''comply with the law. People's constitutional rights are being violated. They can't do this to people.''

Burghardt said the protesters, who slipped onto the sprawling areas before dawn Thursday, endangered themselves and searchers who hunted for them because there are unexploded bombs on the ranges.

''They succeeded in closing down our ranges. But at the same time they succeeded in undermining the combat readiness of Navy personnel,'' he said.

The protest by foes of expanded military operations in central Nevada delayed training involving 57 planes. The fourth range used by Fallon already was shut down.

The Navy suspended bombing practice on the Bravo 20 range last month to clean the range, officials said. Protesters camped there aren't being removed pending resolution of a dispute over control of the range.

But Burghardt said that anyone caught on the reopened Bravo 16, 17 and 19 ranges would be removed because the training areas ''are directly and undisputedly under Navy control.''