Biddeford city officials are increasing inspections at Clifford Park after a series of fires there in the past week.

Two of three fires in Clifford Park since Sunday were connected to illegal campfires, prompting new daily patrols to look for violations of city ordinances against fires and camping in the park. The fires have posed a challenge to firefighters, as they burn underground and pop up in unburned areas of the 140-acre forested park in the middle of the city.

Members of the Friends of Clifford Park have found evidence of campfires and campsites numerous times in the past two years and reported them to city officials, but it wasn’t until Sunday that a fire spread beyond a fire pit.

“I’m not surprised there was a fire because it was just a matter of time,” said Catherine Glynn, who lives near the park and is chairperson of the friends group.

Fire Chief Scott Gagne said the first two fires were located close together, but a more stubborn fire that burned Wednesday was in a different part of the park. Two of the fires, including the one Wednesday, were caused by campfires left unattended, he said. That fire was spotted by a fire department dispatcher who saw the smoke through a camera and by a pilot flying over the area.

“All have been in difficult spots to get to, but yesterday’s was the most challenging as far as location,” Gagne said Wednesday as fire crews continued to look for and put out hot spots.

The fire scene is near the top of Clifford Park, in a rugged forested area with no major trails through it. Firefighters had to climb over rocks and boulders carrying backpacks full of water, hundreds of feet of hose, and portable pumps. Gagne said crews from Biddeford and Saco used 6,000 gallons of water on Wednesday, then had to return to the scene that night and throughout the day Thursday. One junior firefighter was treated at a local hospital for dehydration.

“It’s much more labor intensive because there’s a lot of digging. The fires burn 4 to 7 inches underground, then move horizontally and pop back up in other areas,” Gagne said.

After multiple campsites were found this week, the Biddeford Codes Enforcement Office is starting daily checks of the park and making arrangements to remove unoccupied campsites.

Roby Fecteau, the city’s code enforcement officer, said his office was notified Wednesday night that campsites had been found in the park. On Thursday, a member of the codes staff found two unoccupied campsites, which city officials are now developing a plan to remove, he said.

Glynn said the Friends of Clifford Park are in the park almost daily to walk, hike or care for trails. Volunteers who come across camp fires have been burying burned material and covering the area with leaves and pine needles to make it look untouched. Several times people have reported coming across a live fire, she said.

“This has been a persistent problem of people burning in the park,” Glynn said.

The public works department has removed campsites and temporary structures from the park, where both camping and camp fires are prohibited by city ordinance. The fires this week should prompt a larger discussion about the proper use of the park, which most people enjoy while being respectful of the rules, Glynn said.

“There are houses that are right on the edge of the park. If the park were to burn, we would lose all of that recreational opportunity,” Glynn said. “People are really fond of their forest within the city. It really feels wild, like you can escape into the woods.”

Gagne, the fire chief, said people should call 911 if they see smoke or fire while they’re walking or biking in the park.

“You can easily have a fire that will burn for hours in there and no one will know it,” Gagne said.