"It's not a natural death and it's not the Prestige," Luis Laria, president of marine protection agency CEPESMA said, referring to a massive oil spill from the Prestige tanker late last year. He declined to speculate on the cause.
Three of the little-known creatures washed up in the area about a year ago and marine biologists said global warming could be to blame for the mysterious deaths.
The giant squid, the mythical monster that attacked Captain Nemo's Nautilus in Jules Verne's "Twenty Thousand Leagues Under the Sea," is the world's largest invertebrate and lives at depths of up to 6,562 feet.
Laria said Spain's Asturias coastal region has one of the world's most important giant squid populations.
The second squid to wash up in recent days was a 191-lb female and was found by a man swimming. He told a Reuters photographer he had attached one of the tentacles to a float and dragged the creature toward the shore.