Police Seeking Motive for Bombings : Crime: Man is in critical condition after device placed in a dumpster blows off his hand. A second explosive is detonated safely.

Los Angeles police investigators were baffled Saturday after one of two bombs left in a dumpster blew off the hand of a man rummaging through the trash and forced the evacuation of scores of residents.

“We don’t have much to go on,” said Detective Tom King of the Los Angeles Police Department’s bomb unit. “No suspects, no motive, no overtones, no prior threats--no nothing.”

Jaime Castaneda, 22, remained in critical condition Saturday as his family kept vigil at Midway Hospital Medical Center. He lost part of his forearm in the explosion Friday afternoon, suffered injuries to his head and chest, and underwent a tracheotomy to ease his breathing, family members said.

“The situation is terrible for the whole family,” said Hugo Castaneda, 26, who helped bring his brother here from Mexico two years ago. “He looks bad. The situation is critical--we just have to wait, but we thank God he’s alive.”

No one else was hurt, but the explosion led the Los Angeles Police Department’s bomb unit to cordon off several blocks of West Pico Boulevard near Koreatown and to evacuate 160 nearby residents in case more explosives were found.

“It was terrible, real inconvenient,” said Clarence Davies, 43, who was ushered out of his apartment building a few hours after the first explosion. “I was just cooking my dinner.”

Using a bomb-detecting “robot,” bomb investigators found a second explosive in the same trash bin. With a remote activator, they were able to detonate it about 4 a.m., shaking the neighborhood and setting off car alarms for blocks.

“It was the loudest I’ve ever heard (detonated),” said Detective Olivia Spindola of the bomb squad.

Castaneda often hawked Latino music cassettes from a cart on street corners around the 3300 block on West Pico Boulevard, near his home. When business was slow, he often rummaged through trash bins looking for cans, pictures, books, spare parts and myriad other items that someone else had deemed worthless, family members and local merchants said.

“He didn’t need the stuff,” said his brother Hugo, who lives with Jaime and three other family members near the site of the explosion. “He just has fun with it.”

As usual, Castaneda was apparently rummaging through a dumpster Friday afternoon at a strip mall on West Pico Boulevard between Van Ness and Arlington avenues, police said. But his latest trash expedition turned tragic about 2:45 p.m., just around the time that school was letting out at the Commonwealth Elementary School across the street.

“He apparently reached inside the dumpster and there was an explosion,” King said. The trauma was massive, he said. “He almost died as they took him to the hospital.”

By early Saturday afternoon, evacuated residents--housed by the Red Cross at area motels and schools--had begun to stream back into the neighborhood, and police were once again allowing traffic through the area. But the remnants of the tragedy remained in the form of police chalk markings and garbage strewn about the parking lot where the bombs went off.

Police are at a loss to explain the bombings.

Speculation from a few investigators focused on the possibility of a homemade explosive discarded randomly. But investigators were also interviewing area merchants to find out if anyone had been attempting to “buy out” their stores--and might want to send a message. Several business people said they could think of no such explanation.

King said the bombing is unusual for its lack of motive. But, he said: “We’ll get it--we have real good luck on these things.”

After the explosion, a worker at a shop next door saw Castaneda writhing on the ground, bloodied, and ran to call 911, witnesses said. Someone wrapped him in a sheet.

Martha Langston, who owns and runs the LaunderLand laundry next to the dumpster, returned to the laundry shortly after the explosion and heard Castaneda screaming in Spanish. “He was asking about his hand . . . (yelling) ‘My hand! My hand!’ ”

Langston said Castaneda would often bring his cart to the strip mall parking lot, selling his Latino music tapes and hiding them next to or even inside the dumpster while he was away. Sometimes, Langston said, she paid him a few dollars to help with store errands.

“He was here like every day,” said Oscar Dominguez, 16, who works in a key shop next to the laundry. “He never bothered nobody.”