The U.S. Coast Guard ordered dozens of vessels away from the site of the massive BP oil spill Thursday as a tropical storm moves quickly toward the Gulf of Mexico.

The order came hours after the U.S. National Hurricane Center in Miami said a cluster of thunderstorms in the Bahamas would move into the eastern and central Gulf in the next few days.

Ships will have to move away from the site of BP's capped oil well in the Gulf of Mexico because a tropical storm is heading into the area. (Dave Martin/Associated Press)Rear Admiral Paul Zukunft directed non-essential ships to move to shore, which he said would "protect [his team's] ability to respond to the dynamic requirements of the incident."

He also ordered crews to remove boom equipment from delicate marsh areas not currently threatened by oil to protect it from being crushed in tempestuous weather.

"The protection of the equipment and crew is paramount to ensure maximum ability to respond to any new challenges a storm may pose to the enormous mission," Zukunft said.

The storm system officially become tropical storm Bonnie on Thursday evening, and forecasters said it could reach the Gulf of Mexico by Saturday.

In Louisiana, Gov. Bobby Jindal declared a state of emergency.

Even if essential ships are ordered to evacuate the area, the temporary cap on BP's ruptured well can stay closed, response commander Thad Allen said.

Growing confidence in the experimental cap's security convinced scientists it was safe to leave it unmonitored for a few days, he said. Officials will decide Thursday evening whether ships will have to leave.

BP timetable in jeopardy

Crews had planned to spend Wednesday and Thursday using cement to reinforce the last few metres of the relief tunnel that will be used to pump mud into the gusher and plug it once and for all.

Part of a containment capping stack is seen in the Gulf of Mexico in this frame taken from a BP live video feed on Wednesday. (BP/Reuters)Instead, BP put the task on hold and placed a temporary plug, called a storm packer, deep inside the tunnel in case it has to be abandoned until the storm passes.

"What we didn't want to do is be in the middle of an operation and potentially put the relief well at some risk," BP vice-president Kent Wells said.

If the work crews are evacuated from the site, it could be two weeks before they can resume the effort to stop the flow of oil. That would upset BP's timetable, which called for finishing the relief tunnel by the end of July and plugging the blown-out well by early August.

Scientists have been scrutinizing underwater video and pressure data for days, trying to determine if the capped well is holding tight or in danger of rupturing and causing an even bigger disaster. If the storm prevents BP from monitoring the well, the cap may simply be reopened, allowing oil to spill into the water, Allen said.

As the storm drew closer, boat captains hired by BP for skimming duty were sent home and told they wouldn't be going back out for five or six days, said Tom Ard, president of the Orange Beach Fishing Association in Alabama.

Workers questioned rig's safety

The cause of the April 20 blast that killed 11 workers and sparked the oil spill is still under investigation, but there have been repeated questions raised by workers over the equipment and safety conditions aboard the rig.

The New York Times reported early Thursday that rig workers said in a confidential survey before the explosion that they were concerned about safety and the condition of some equipment on board.

A spokesman for Transocean, the owner of the rig leased by BP, confirmed existence of the reports to The Associated Press.

The Times reported that another report conducted for Transocean by Lloyd's Register Group found that several pieces of equipment — including the rams in the failed blowout preventer over the wellhead — had not been inspected since 2000, despite guidelines calling for inspection every three to five years.

Transocean said most of the equipment was minor and the blowout preventer was inspected according to manufacturer guidelines.

With files from The Associated Press