SCRANTON, Pa. (AP) — A Pennsylvania elementary school closed for the day after educators realized that a man had entered the building overnight, 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 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 parts of the school.

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. It is expected to reopen Friday.