RAMONA, Calif. (AP) _ Someone left four kittens inside a sealed box outside a bank, and a sheriff's department bomb squad fearing foul play exploded it, killing three of the animals.

''It was just a horrible thing to see,'' said Sgt. Conrad Grayson of the sheriff's arson bomb squad after authorities discoverd their mistake Monday.

The lone survivor showed no signs of injury Tuesday, a veterinarian said.

Authorities first suspected that a bomb might be inside the tightly wrapped box left outside the Home Savings of America office Monday morning in the northen San Diego County city, Grayson said.

After determining that there was no bomb, an X-ray was taken, showing a soft shape with bones.

Squad members suspected that the shape might be that of a rattlesnake, in part because of a recent incident in which a man left a rattler inside a box for his mother to find, Grayson said.

The officers decided the safest thing to do was blow up the box, he said.

The box was blown up about 11 a.m. Three kittens died instantly, and the fourth, a female believed to be one month old, suffered no physical injuries.

''She's doing absolutely great,'' veterinarian Peggy Fischer said of the kitten, dubbed Lucky.

''She was probably the fourth in line closest to the explosion,'' she said.

The Avocado Animal Hospital has had a half-dozen offers of homes for Lucky, but the domestic cat probably will go to one of the bomb squad members, she said.

Grayson said it was not known who left the box or why.