Four “suspicious” fires were reportedly set in Concord on Sunday at the post office, National Park and a swim center, according to officials who have identified a person of interest for the alleged arson spree.

Investigators outside of Concord District Court also found items that were possibly related to the other fires. No fire was reported at the courthouse on Sunday.

First responders initially at noon received reports of a fire at the Beede Swim and Fitness Center at 498 Walden St., which is located on the campus of Concord-Carlisle Regional High School.

Upon arrival, crews found two fires — one of which was behind the swim center and the other was located in front of the center.

Then about 30 minutes later, Concord Police and Fire received another report of a fire at the U.S. Postal Service at 34 Walden St.

The fourth fire was reported about 30 minutes later at a shed on National Park property at 955 Lexington Road.

No injuries were reported in the four fires.

“At this time the cause of the fires has been deemed suspicious and is under investigation by Concord Police with assistance from the National Park Service, the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF), Massachusetts State Police, and the State Police Fire and Explosion Investigation Unit attached to the State Fire Marshal’s Office,” officials said in a statement.

Investigators have identified a person of interest. That person was not immediately named by authorities.

All incidents remain under investigation.