WASHINGTON — Senate officials lifted some restrictions on their side of the U.S. Capitol complex Monday while authorities searched for a potential second suspect in the Navy Yard shootings.

Sergeant at Arms Terrance Gainer restricted people from leaving or entering Senate buildings for part of the day. By late afternoon, he said people would be allowed to leave the buildings but only senators and staff would be allowed to enter before Tuesday.

Earlier in the day, Gainer said he had no information to suggest the Senate, its members or staff were in danger but restricted access and exits to the buildings out of an abundance of caution.

“We have too little information on the possibility of additional shooters,” Gainer said in an email. In a memo to Senate personnel, Gainer said the policy would remain in effect “until we deem the situation safe in the neighboring community.”

The House side of the Capitol complex, which is closer to the Navy Yard, remained open.

Senate Majority Leader Harry Reid, D-Nev., announced that the shootings a little over a mile south of the Capitol had prompted him to adjourn the Senate and postpone votes until Tuesday.

Authorities said as many as two gunmen opened fire Monday morning inside the nearby Washington Navy Yard, killing at least 12 people in an attack on office workers at the heavily secured military installation in the nation’s capital. One gunman was dead and police hunted for a second possible attacker.