TOKYO — A heavily damaged reactor building at the tsunami-stricken Fukushima Daiichi nuclear plant has a slight tilt, but the tilt does not pose a risk to the integrity of the building, according to the plant’s operator.

The Tokyo Electric Power Company, or Tepco, said in a report on Monday to Japanese nuclear regulators that at least two of the walls of the No. 4 reactor building are bulging outward at various points and that the building is tilting. The biggest bulge measured about 1.8 inches about a third of the way up the building, the report said.

The latest findings could add to concerns over the state of the No. 4 reactor building, which houses on its upper floors a cooling pool filled with 1,331 spent and 204 unused nuclear fuel assemblies. Each assembly contains approximately 50 to 70 rods.

Some experts say that the building — ravaged in a hydrogen explosion in the early days of the disaster in March 2011 — is not strong enough to support the fuel pool, especially if another earthquake hits the region.