Associated Press Writer

HOUSTON (AP) A fire at a well-known Houston furniture store that caused up to $20 million in damage was an arson, officials said Thursday.

Investigators have ruled out all accidental causes of the May 21 blaze at the warehouse at Gallery Furniture, said Robert Elder, the special agent in charge of the Bureau of Alcohol, Tobacco, Firearms and Explosives' National Response Team.

Elder said investigators have looked into 100 leads. But he declined to discuss other details of the case, including how the fire might have started or where exactly in the warehouse it began, citing the ongoing investigation.

The store's owner, Jim "Mattress Mack" McIngvale, is among Houston's most successful entrepreneurs and one of its biggest philanthropists.

Elder said McIngvale has cooperated with the probe.

"Mr. McIngvale has been very generous with investigators," Elder said. "Until we know for certain who did it, we don't want to eliminate anyone" as a suspect.

McIngvale later said he was shocked and stunned the fire has been ruled an arson.

"Obviously we had prayed this would not be the outcome," he said at his other store in Houston's upscale Galleria area. "All we want is this person to be caught and brought to justice."

More than 100 people were in the warehouse and adjacent furniture showroom when the fire broke out, but all escaped without injury. More than 100 firefighters responded.

"We're very, very fortunate we did not have someone injured or killed," Elder said.

McIngvale said he hopes to partially reopen the store by July 4.

McIngvale and his wife Linda first opened the store at an empty model home park in 1981, with just $5,000, sleeping there to guard their four sofas.

McIngvale whose high spirited and sometimes comic TV and radio spots are well-known in the Houston area is also a big supporter of athletics. He co-owns Westside Tennis and Fitness Club, which has hosted the U.S. Men's Clay Court Championships.

In 2006, he made headlines when he forced officials at the University of North Texas in Denton to rename its new athletic facility after the football coach the school had just fired or have McIngvale's $1 million gift redirected to the music department.

Copyright 2009 The Associated Press.