HONOLULU -- Seven clams were returned Saturday, about a week after they were stolen from the Waikiki Aquarium, officials said.

The clams were taken from an outdoor display designed to give children a closer look at the sea creatures.

The clams were found in a Tupperware container with water and gravel in a shopping bag in the aquarium's theater.

"(It's) probably the worst place in the aquarium they could have dropped them off because it's air conditioned, so the temperature of the water in the container was very low," Waikiki Aquarium Director Dr. Andrew Rossiter said. "Six of the seven look to be OK. One of them looks ill at the moment."

The seven stolen clams are about 1 inch to 4 inches wide.

Some of the clams have the capability to grow to giant size. The aquarium planned to breed them, but the stolen ones were years from breeding age.

Because the clams are endangered, people must have a license to own them.

"Presumably a hobbyist took them to put in their own exhibit, or to sell on the black market because as you know, it is illegal to own or sell these animals in Hawaii," Rossiter said.

After the theft, the aquarium put the other 37 clams into hiding. They won't be put out again until the display can be rebuilt so it is more secure.