There are concerns about further delays to the opening of the National Children's Hospital.
It has emerged works are needed to improve air circulation.
The facility has faced setback after setback, and today another one has emerged.
Sinn Féin says works are needed in the ceilings of 11 operating theaters.
It says this could cost €50 million to fix and delay its completion, which is set for next March 2024.
"This is a hospital that is now the most expensive in the world.
"We've had crisis after crisis, cost overrun, after cost overrun.
"We've had a hands-off approach from this government for far too long.
"We had a PWC report a number of years ago, which raised very serious governance issues.
"And now we have a situation where this isn't just 11 ordinary rooms."
But the Pediatric Hospital Development Board is insisting the works are minor.
Health Minister Stephen Donnelly is also downplaying the issue, saying, "nothing has been agreed.
"All that has happened is the Hospital Development Board is considering potential changes to 11 out of 5,000 rooms in the hospital."
Sinn Féin says it has documents to prove its claims.