$2.5-Million Painting Goes Up in Smoke on Freeway : Art: A work by Mark Rothko is destroyed by a fire while being carried in a moving van.

A painting by Mark Rothko valued at $2.5 million was destroyed when the moving van transporting it caught fire on the San Bernardino Freeway in Baldwin Park, sheriff’s deputies said Friday.

No one was injured in the blaze, which broke out Thursday about 9 p.m. in a van owned by Professional Packers & Forwarders Inc., a Los Angeles-based moving company that often ships paintings for art dealers.

Also destroyed were a wood relief by contemporary artist Frank Stella, valued at $150,000, and assorted antique furniture, valued at $350,000, officials said. Arson investigators, who concluded that the blaze was accidental, said the art was being transported from a private dealer near Palm Springs to a Beverly Hills auction house.

Initial reports were that the damaged painting was the work of 19th Century Dutch master Vincent van Gogh. But Sgt. Ron Moya, an arson investigator with the Los Angeles County Sheriff’s Department, said the label on the frame indicated it was by Rothko, a leading exponent of Abstract Expressionism in the 1950s and ‘60s.

The title of the painting, which measured 35 by 60 inches, is not yet known.

“It was just a limp rag by the time we took it out of the truck,” Moya said. “I couldn’t make any image at all. It was just burnt canvas.”

Rothko, who was born in Russia and emigrated with his family to Portland, Ore., as a child, killed himself in 1970 at age 66. His richly colored paintings, most of which are composed of large fuzzy-edged rectangles, helped turn world attention on the American art scene.

His paintings hang in museums around the world, including the Museum of Contemporary Art in Los Angeles, which purchased seven of them in 1984.

“It’s a sad loss,” said William Wilson, The Times’ art critic. “A work by a great artist, whether Rothko or anybody else, is irreplaceable. . . . It’s just about the only thing in the world that is irreplaceable.”

Documents in the cab of the truck, which was driven by Jeffrey Johnson, 32, of Marina del Rey, put the painting’s value at $2.5 million. A spokeswoman for Professional Packers declined to say who owned the work, which was headed to Sotheby’s in Beverly Hills and was ultimately to be auctioned by the firm’s New York office.

“We are very disappointed,” said Andrea van de Kamp, managing director of Sotheby’s local office. “Obviously, we’re going to be looking into the matter.”

Motorists saw smoke coming from the back of the 30-foot truck as it was westbound on the freeway, and signaled the driver to pull over, Baldwin Park Police Lt. Mike Bennett said.

The driver pulled off the road and tried to put out the fire with an extinguisher he carried in the cab but was unsuccessful, Bennett said.

Although the blaze originally was labeled as suspicious, arson investigators now believe it was caused by faulty wiring in a light in the trailer’s roof, Moya said.