Missile Mishap Closes Bay : Munitions: Unarmed weapon slipped while being unloaded. No one was injured, but Anaheim Bay and Huntington Harbour were closed as a precaution.

Anaheim Bay was closed to the public for about an hour Thursday morning after an unarmed guided missile slipped from its launcher aboard a warship at the Seal Beach Naval Weapons Station and cracked its plastic tip.

Navy officials said the accident, which occurred during unloading of munitions on the frigate Jarrett, caused no explosion or injuries and only slight damage to the surface-to-air missile. It was described as a minor mishap.

At the request of the Navy, the Orange County Sheriff’s Harbor Patrol blocked pleasure craft from access to Anaheim Bay and Huntington Harbour from 9:54 a.m. to 10:55 a.m. The Navy’s safety rules require that the area be immediately closed to the public when an abnormality occurs during loading or unloading of explosives.

“Any time you have an explosive device that gets rough handling, you have to be very cautious,” said Al Christopher, executive director of the naval base. “But as we expected, there was no hazard.”

It is the first time that the Navy had to close the popular harbor.

The missile’s radome, a cone-shaped plastic piece that protects radar equipment in the nose, was cracked from the impact of hitting a handling cart on the ship’s deck. No damage occurred in the rear of the missile, where explosive material is stored.

“It was on the launcher ready to go to the handling cart and into storage, when it slipped down and hit the cart hard, cracking the radome,” Christopher said.

Naval officials from the weapons base and the ship, which returned from duty in the Persian Gulf last month, were investigating. Christopher said they didn’t know yet if the accident, which occurred alongside the base’s pier, was caused by equipment failure or human error.

The ship’s crew was unloading munitions at Seal Beach before heading to its home port at Long Beach Naval Station.

Although the 2,000-pound Standard antiaircraft missile was unarmed, the ship’s crew and an estimated 20 to 30 naval workers at the wharf were moved to a safe distance for about an hour.

“When anything like that happens, we stop operations and make sure everything truly is safe. You try to minimize the hazard by getting unnecessary people away, and then you inspect it,” Christopher said. “There wasn’t that much concern. . . . If an explosion was going to happen, it would have been instantaneous.”

The missile, about 10 feet long and more than a foot in diameter, will be repaired. The missile costs $769,000 to manufacture, according to the 1991 Department of Defense budget.

Base officials could not recall any similar mishap at Seal Beach, despite continuous loading and unloading of explosives. The base, built in 1944, is the Navy’s chief southern West Coast port for moving munitions.

Seal Beach council member Gwen Forsythe said she was assured by the Navy that even if an explosion had occurred, nearby residents would not have been harmed. But she said city officials will explore the incident.

“We’ve been told that at no time was any of the area in danger, and they did take all precautions. But it certainly raises my concern,” Forsythe said. “I need to know exactly what happened and who was at fault and what we can do from now on to prevent it from happening again. . . . I think we were extremely lucky.”

Safety devices are built into the missiles to minimize the risk of explosion during handling.

“Back in World War II, there were some explosions at bases that were thought to result from rough handling of munitions. But there have been changes in the explosives formulations since then and more safety devices installed,” Christopher said. “There are always possibilities of explosion. . . . Things can happen but it would be extremely unusual.”

Nearby boaters could see a crew unloading missiles from a Navy frigate docked underneath a red flag about one-third of a mile west of the bridge at Pacific Coast Highway. One said he thought it was unusual, because he normally sees munitions being loaded onto ships at the site, not taken off them.

“I’ve never seen them offload before, and I’ve been in this harbor for 10 years,” said Jim Hildreth, a local pleasure boat craftsman and sailing enthusiast.

The Sheriff’s Harbor Patrol blocked a handful of boats from crossing under Pacific Coast Highway. Three or four boats also were prohibited from entering Anaheim Bay, on their way to docks at Huntington Harbour and the adjacent Sunset Marina.

Times staff writer David Willman contributed to this report.