Two of the five killer whales captured off the coast of Wakayama Prefecture in February have died at an aquarium there, according to civic groups working for their return to the sea.

The youngest of the five whales, a 2- or 3-year-old male, died June 14, said a representative of the Dolphin and Whale Action Network. The second, a female reported to be pregnant when captured and which may have miscarried in April, died June 17, the group said.

The network and two other animal rights groups submitted a request June 17 to concerned government agencies and the aquarium for details on the whales covering the period up to their deaths. The groups also urged the release of the three remaining orcas and asked for cooperation in abolishing the capture of ocean residing mammals.

A local university is conducting autopsies to determine the cause of the deaths. The Wakayama Prefecture Fisheries Division said it was informed by the aquarium of the death of a male orca June 14 and that another died early June 17.

A representative of Adventure World, the aquarium where the orcas are being held, did not comment on the health of the whales. "All I can tell you is that we are committed to breeding the orcas and have no intention of using them in shows or public displays."

The five orcas, captured near Taiji, Wakayama Prefecture, were selected from a pod of 10 that were rounded up and trapped in a bay. The controversial capture, which is banned internationally but was authorized by the Fisheries Agency for "research purposes," drew domestic and international condemnation.