A two-alarm fire gutted a basement storage room in Mount Olivet United Methodist Church in Arlington early yesterday, 24 hours after a series of small fires and vandalism in the church. Fire officials said they believe the incidents are related and have determined them to be arson.

Yesterday's blaze, which caused about $175,000 damage to the church at 1500 North Glebe Rd., was larger and more destructive than four small fires set in various rooms of the church and discovered by a custodian Wednesday morning.

The first fires, set with papers, telephone books and toilet tissue, "were really childish, prankish-looking," said Arlington Fire Department spokesman Steve Hynson. "But today is a different story. The people that did this did a very thorough job of starting a major fire . . . . based on what was seen yesterday, we assume that they're connected."

Hynson said fire officials had not determined a motive for the fires or vandalism. "None -- other than revenge, a get-even type of thing," Hynson said.

Bill Thomas, pastor of the 132-year-old church, said he arrived with a custodian about 8 a.m. Wednesday to find a pile of toilet tissue and other papers smoldering in the first-floor fellowship hall. They discovered three smaller fires elsewhere in the church had burned out, he said.

Church and fire officials said there was other evidence of vandalism: paint spilled on the carpet and on choir robes, furniture overturned, papers strewn on the floor and fire extinguishers emptied.

Fire officials said there was no sign of forced entry to the building either time.

Yesterday's blaze, which took 45 minutes to extinguish, destroyed most items in a 12-by-20-foot storage room. Other parts of the building suffered smoke and water damage, and an Arlington building inspector declared the church unsafe yesterday because asbestos particles may have been released by the blaze.

"The damage was very slight, relatively speaking, except we were frustrated by someone wanting to burn the place down," Thomas said.

"I can't think of any reason at all why someone would want to do anything like that," the minister said. "As far as why it happened or who caused it to happen, I'm blank. I don't really have any idea."