Authorities are continuing their investigation into a recent string of fires that appear to have been set intentionally.

Detectives with the Ellis County Sheriff's office and an investigator from the Kansas State Fire Marshal's office were back in the field Friday, examining the scene of at least 15 fires that were set in less than a week.

Ellis County Rural Fire Chief Richard Klaus said they still haven't ruled out the possibility a fire Tuesday -- burning 25 acres and threatening a home -- might be among the string of fires.

"We don't know yet," he said. "We're keeping all our options open."

"It's still under investigation," Ellis County Sheriff Ed Harbin said of trying to determine who might be responsible for setting five fires on March 6 and another 10 Wednesday.

Most of Wednesday's fires involved grass and trees, but an old granary was damaged in one fire.

In the first round of fires, the damage was more extensive, with damage to an all-terrain vehicle, a jet ski, a horse trailer and bales and then a storage shed and trailer house used for storage.

All of the fires have been located outside Ellis County cities, drawing crews from the Ellis County Rural Fire Department.

Harbin said the investigation now is getting assistance from the Kansas Highway Patrol.

Klaus declined to say what evidence was found Thursday when investigators were first at the scene of the string of 10 fires, ranging from those northwest of Hays to southeast of Hays.

"I think they're out going to the scenes and getting any evidence, if there is anything," Harbin said of the situation Friday.

In the meantime, Harbin still is asking anyone to contact the sheriff's office if anything suspicious is spotted in rural areas.

"We'll take any information we can get," he said.

The Elllis County Sheriff's office can be contacted at (785) 625-1040.