Two phoned-in bomb threats claiming an explosive device was on the destroyer USS William P. Lawrence in the shipyard’s Dry Dock 4 led to a lengthy Joint Base Pearl Harbor-­Hickam lockdown Tuesday, bottling up thousands who were told to shelter in place and avoid windows in the event of flying glass, officials said.

Personnel working in Dry Dock 4, where repairs on surface ships are conducted mainly by contractors, were evacuated to Dry Dock 1 during the lockdown, officials said.

Bomb-sniffing dogs could be seen working along the waterfront. No bomb was found, the joint base said. Motorists who were not able to leave the base for hours due to the lockdown vented their frustration on social media.

At 9:39 a.m., entrances were secured and the shelter-in-place order was given for what the base referred to as a “security incident.”

An “all clear” canceled the security watch at about 1:30 p.m. At about 1:45 p.m. the joint base posted to Facebook, “No hazardous conditions exist. Resume normal operations.”

A “person of interest” was sought, questioned and found to have no involvement, an official said. Honolulu police and the Federal Fire Department responded to assist with joint base security personnel.

Tours to the USS Arizona Memorial and other museums at Pearl Harbor have resumed, the base said in a release.

“During the investigation, those tours were suspended, and guests at both the USS Missouri Memorial and the Pearl Harbor Aviation Museum on Ford Island sheltered in place as well,” the base said.

“We are grateful to the first responders who helped us investigate and secure the potential incident,” Col. Tammie Harris, deputy joint base commander, said in a release. “I want to assure everyone that we will do everything possible to maintain the operational readiness of JBPHH while protecting the safety of our base employees, our service members and their families.”

On March 9 the Hawaii Regional Maintenance Center docked the William P. Lawrence in Dry Dock 4 for maintenance. The approximately $90 million job is expected to include a major combat systems installation.

Ironically, the joint base had warned of the sound of gunfire due to training in an annual exercise called “Citadel Protect” that started Monday and provides anti-terrorism and “force protection” training for Pearl Harbor sailors.

Because of the planned exercise, confusion resulted as to the source of the lockdown.

“Beginning TODAY, Tuesday, June 8, the training will involve the use of blank rounds fired from crew served weapons such as M240s (belt-fed machine guns) in the vicinity of the harbor. Base personnel, residents and those who live near the installation should not be alarmed by the sounds of gunfire, other popping noises and activations of the base-wide Giant Voice System,” the joint base said on Facebook.

A news release said, “Residents and personnel who live and work on (the joint base) may see increased traffic and delays in base access. The exercise involves various training scenarios that replicate real-world events, and is designed to enhance the readiness of Navy security forces to respond to threats to installations and units.”

The training was halted when the real-world base security concern emerged.