The United States Capitol will begin formally reopening to visitors and tourists on Monday, after being closed to the public for about two years because of the coronavirus pandemic and security concerns after the Jan. 6 riot.

A limited reopening will start March 28 with lawmaker-led tours and staff-led tours of up to 15 people as well as a limited number of school tours, according to a memo from William J. Walker, the House sergeant-at-arms, and Dr. Brian P. Monahan, the attending physician. Tours of the Capitol Dome for up to eight people will begin April 25, and the Capitol Visitors Center will fully open at the end of May.

“We appreciate your continued patience and cooperation as we work together to resume public tours of the Capitol for the American people in a way that protects the health and safety of visitors and institutional staff alike,” Mr. Walker and Dr. Monahan wrote in the memo.

The two men said the phased reopening was coordinated with congressional leadership, the U.S. Capitol Police Board, the Capitol Police and other leaders.

The Capitol has seen an uptick in visitors in recent weeks, even before the announcement was made. The formal reopening comes as pandemic restrictions loosen across the country and just weeks after House leaders announced that masks would no longer be required in the chamber, regardless of vaccination status. The White House said last week that public tours would start in April, after being closed to the public because of the pandemic.

Republicans, many of whom eschewed mask-wearing and other pandemic restrictions long before this year, have pushed for Democratic leaders to agree to reopen the building. But there have been a flurry of recent coronavirus cases on Capitol Hill, with Senator Bob Casey, Democrat of Pennsylvania, announcing a positive test on Tuesday.

The Capitol first shut down in March 2020, but its reopening has been delayed as new variants swept through the country and security concerns increased after the Jan. 6 riot. The ranks of the Capitol Police were depleted after the attack, as officers recovered from the mental and physical trauma they suffered defending the building.