SCRANTON (AP) — A Pennsylvania elementary school closed for the day after educators realized that overnight a man had entered the building, got naked and spilled Murphy Oil Soap on the gym floor.

Neil Armstrong Elementary School staff originally thought the spilled soap was a prank, but the principal reviewed security tape footage and saw that a man had been on the premises.

Scranton Police Chief Carl Graziano says that once inside the school, the man took off his clothes and walked through at least a portion of the school while naked.

School officials decided at about 7 a.m. to close the school for safety.

Graziano says there were no signs of forced entry.

More than 600 students are enrolled at the school, which is expected to reopen Friday.