Law enforcement divers recovered six commercial-grade blasting caps at the bottom of Huntington Harbour on Wednesday, and authorities were investigating how the explosive devices got there.
The caps, which require a charge to detonate more powerful explosives such as plastique or dynamite, were not a threat to homes or boats that line the harbor, said Orange County sheriff's spokesman Jim Amormino.
Nevertheless, authorities asked nearby residents not to use cellphones for fear that an electronic signal would trigger the caps, which were found scattered in water about 15 feet deep. The ban was in effect from 9 a.m. to noon and lifted when authorities determined that the threat of explosion was minimal.
"Our main concern initially was that the caps were attached to an explosive device," but no such explosives were found, Amormino said.
Commercial divers hired by the Huntington Harbour Property Owners Assn. told officials they saw about eight of the devices Tuesday while doing an environmental survey of the residential area's waterways, which lead to the ocean. They also marked the location.
How the detonators ended up in the water remained a mystery late Wednesday. Authorities estimated that the devices -- each about the size of a cigarette and attached to a wire about 10 feet long -- had been in the water no more than 48 hours because of the absence of corrosion. Investigators determined that the caps did not come from the Seal Beach Naval Weapons Station.
The caps were found near Bonaire Circle at the eastern end of the harbor. Amormino said six caps had been recovered by 3 p.m. and the divers were looking for more.
Residents watched the divers from balconies and sidewalks with a mixture of amusement and concern.
"We thought it was terrorists," said Mark Stanfield, who rushed over to be with his sister, a Huntington Harbour resident.
His niece, Ashley Greer, 14, said the incident was "exciting but scary."
"You don't expect this to happen here," she said. "There's police cars and firetrucks everywhere."