(Reuters) - Oregon’s State Capitol building was shut down on Saturday as a safety precaution, police said, in the wake of a bitter partisan divide that had Republican lawmakers walked out to block a vote on a bill to reduce climate change-causing gases.

Oregon Governor Kate Brown speaks at the state capital building in Salem, Oregon , February 20, 2015. REUTERS/Steve Dipaola

Democratic Governor Kate Brown on Thursday dispatched state police to round up the absent 11 Senate Republicans, at least two of whom are needed to form a required quorum for conducting business in the 30-member chamber controlled by Democrats.

Some right-wing militia groups have expressed support for the absent Republican lawmakers, and opponents of the bill to cut greenhouse gas emissions below 45 percent of the state’s 1990 levels by 2035 staged a small rally on Saturday at the Capitol building in Salem.

“We have been monitoring information throughout the day that indicates the safety of legislators, staff and citizen visitors could be compromised if certain threatened behaviors were realized,” said Oregon State Police spokesman Captain Timothy Fox said by email.

Fox declined to elaborate on the threats, other than to say: “We are monitoring all sources of information and intelligence.”

The decision to close the building came after Senate President Peter Courtney canceled a floor session he had previously set for Saturday because of risks posed by the possible presence of militia groups, his spokeswoman, Carol Currie said by phone.

The Republican walkout has halted work on other legislation as well, she said.

Although no Republican senators have been apprehended so far, Fox said police have been in contact with several of them and have been assisted by “out of state resources.” He declined to elaborate.

In a “call to action” on Thursday, a militia group known as Oregon Three Percent said it would provide security, transport and refuge for the absent Republican senators.

“We will stand together with unwavering resolve, doing whatever it takes to keep these senators safe,” the group said on its Facebook page.

Republicans contend the legislation, which would cap the state’s total amount of greenhouse gases and force utilities and other companies to buy emission allowances, would make fossil fuel prices too high. They have instead sought to allow the proposal to be placed before voters on a ballot.

One of the missing Republicans, state Senator Brian Boquist, told Portland television station KGW on Wednesday that if state police come for him, they should “send bachelors and come heavily armed.”