A Midtown hi-rise whose support beams were discovered buckling Tuesday is “shifting’’ and in danger of partially collapsing — a situation so precarious that crews can’t even go in to stabilize it, authorities said.

The 37-story former Pfizer headquarters on East 42nd Street —  which is being converted from commercial to residential use — was dramatically evacuated during the morning rush along with seven surrounding buildings when the terrifying safety breach was discovered.

“The concern is that since we have been on site in the early morning, we have seen continued shifting of the structure,” Mayor Zohran Mamdani said early Tuesday afternoon.

FDNY crews and other emergency responders have monitoring the building with sensitive equipment and chillingly discovered the precarious situation, the mayor said.

“The way this building is constructed, it’s a steel-frame building, so it would not be a total collapse, it would be more of a localized collapse,” said FDNY Chief of Operations John Esposito.

“That remains our concern – that it’s moving.”

When asked if that means the building could collapse into itself like a pancake, Esposito responded, “Possibly.”

The news conference also revealed other heart-pounding new details about the harrowing situation far above Midtown.

NYPD and FDNY officials have instituted a “frozen zone from East 40th to 45th streets between First and Third avenues, barring all pedestrian and vehicle traffic for fear the building could collapse.

Mamdani said two structural columns have buckled inside the building’s 21st floor, while another one shows movement.

“The building remains unstable,” he said.

The building and is considered one of the largest commercial-to-residential conversion projects nationwide.

Contractors had been adding 11 new floors on top of a 22-story section of the building, said city Buildings Commissioner Ahmed Tigani.

Sources said the compromised sections appear to be the 17th and 21st floors, below the additions.

Tigani said cause will be investigated, but it’ll first have to be made safe.

“This is a minute-by-minute assessment,” Mamdani said, as he warned New Yorkers to stay away.