A water valve broke in the State Office Building early Thursday, flooding the structure that normally houses legislators and their staffs.

The rupture above the fourth-floor ceiling on the east side of the building went undetected until 5 a.m., according to Curt Yoakum, spokesman for the Department of Administration, which manages the Capitol complex. The break caused significant water damage, especially to the second and third floors, he said.

A company that specializes in water damage is assessing the situation and beginning cleanup.

Staff and legislators were sent home so the cleanup and assessment could begin; offices on the west side of the building appear to be undisturbed.

Because electricity remained on during the cleanup, legislators and staff were warned not to walk in standing water or touch electrical cords. The building was expected to be open Friday, but phone and network access could be interrupted, according to an e-mail sent to staff from the House sergeant at arms.

The building, which is more than 80 years old, was already in a state of disrepair.

The state Department of Administration has said the building needs $100 million in repairs, even before Thursday's water damage.

A 2012 consultant's analysis found a number of problems that often beset older buildings, from insulation to plumbing, electrical, heating and cooling, concluding that "many of the building components and control systems are beyond their rated life expectancy, causing higher operating and repair costs and risking failure."

A $100 million renovation is unlikely, however, as lawmakers are skittish about spending on a building for themselves. The new Senate Office Building and its $90 million price tag have been an ongoing political headache for the DFL, which controlled both chambers of the Legislature when the building was approved in 2014.

Republicans hammered the DFL during the 2014 election over the Senate building, citing it as an example of wasteful spending.

The Capitol is currently undergoing a $300 million renovation.

The Associated Press contributed to this report.

J. Patrick Coolican • 651-925-5042