The United States Coast Guard has ordered the Steamship Authority and Hy-Line Cruises to increase security measures on their ferries following the terrorist bomb attacks in London last Thursday.

Coast Guard officials said they are not sounding an alarm, but are simply taking necessary precautions following the London attacks, which as of mid-day yesterday had accounted for 52 deaths.

"We don't have any specific intelligence that indicates any type of threat against the ferries, but it's prudent, as I'm sure you can imagine, to increase security," Coast Guard petty officer Luke Pinneo told the Boston Globe this week.

The Coast Guard is now providing escorts for some SSA ferries on both the Vineyard and Nantucket runs. SSA passengers traveling over the weekend also noticed the stepped-up security, which among other things included more random searches of foot passengers.

On Thursday, the Coast Guard sent notification to operators of more than 300 large passenger vessels in the United States, including both the boat line and Hy-Line, a private ferry company based in Hyannis, to increase security.

The SSA and Hy-Line ferries together carry about 3 million passengers a year between the mainland and the Islands of Martha's Vineyard and Nantucket. The SSA also carries more than 500,000 automobiles and trucks between the mainland and the two Islands.

SSA general manager Wayne Lamson said yesterday that Capt. Roy Nash, Coast Guard captain of the port at Providence, notified boat line security director Larry Ferreira late Thursday of the need to increase security at the SSA operations. Mr. Lamson said the Coast Guard raised the Marine Security, or MARSEC, level from level one, or elevated, to level two, or high. Level three, or severe, is the highest security level.

The SSA increased its security according to a prearranged plan.

Measures put into effect by the boat line include the use of holding areas for passengers who have cleared security but who have not yet boarded the ferry, a bomb-sniffing dog, the use of mirrors to check under vehicles, increased security checking of luggage and passengers, and identification checks.

Even before the London bombings, Coast Guard boats were providing regular escorts for ferries on the Woods Hole-Vineyard Haven route. Coast Guard spokesman Daniel Kleberg said boats from Woods Hole escorted the ferry Islander on a round trip on July 2 and again on a round trip on July 3.

At the time, Mr. Kleberg said the escorts were not in response to any specific threats, but were a way to provide more overall security.

Yesterday, Mr. Kleberg declined further comment on security measures in the Cape and Islands area.

Mr. Lamson said the Coast Guard provided at least one escort this past weekend between Woods Hole and the Vineyard. He declined comment on whether the Coast Guard has been providing escorts on the Hyannis-Nantucket route.

Coast Guardsmen also have been traveling on SSA vessels as a way to provide more security.

Captain Nash traveled to Woods Hole this past weekend to examine security measures, Mr. Lamson said.

The increased vigilance comes against a backdrop of longer-range SSA plans to install security cameras on its ferries. Despite objections by the former Vineyard representative, the late Kathryn A. Roessel, the boat line board last year approved the installation of the cameras.

Late last month, the boat line issued an invitation for bids to install a closed-circuit security surveillance system on four ferries. The invitation did not identify the specific vessels. The work was to be completed no later than Oct. 14.

Mr. Lamson said the SSA withdrew the bid invitation because of security concerns. The boat line now plans to piggyback its proposed work on another government contract that will be fulfilled by a provider already cleared by the government.

Phil Scudder, vice president of marketing for Hy-Line, said his company is also following MARSEC guidelines for increased security. Mr. Scudder said the procedures, which include checking luggage and some use of a metal detector wand, are adding a little more time to the loading process. Mr. Scudder said the increased security has not affected schedules for Hy-Line vessels.*

He recommends that passengers arrive at the Hy-Line terminals 30 to 45 minutes ahead of departure, to allow adequate time for pre-boarding screening.

Mr. Scudder said he did not know of any vessel escort provided to Hy-Line vessels, but he said a Coast Guard security detail rode the Lady Martha, the Hyannis-Oak Bluffs fast ferry, on at least one trip on Sunday.