But U.S. District Judge Rosemary M. Collyer issued a temporary restraining order barring the export of any additional ships overseas until the government can show it has complied with all environmental regulations.

The ruling comes as a partial setback to the U.S. Maritime Administration, which signed a contract to send 13 of the environmentally hazardous reserve ships to a British scrapper. Environmental groups had filed suit to block the ships, citing safety concerns in towing decrepit vessels laden with toxic PCBs across the Atlantic Ocean.

In a 10-page order, Collyer raised concerns that the Maritime Administration may have failed to abide by regulations governing the export of hazardous material.

In particular, she said the Toxic Substances Control Act "appears to require" the government to obtain an exemption from a regulation banning the export of PCBs. The Maritime Administration received only a letter from the Environmental Protection Agency saying it would not enforce the law. The letter stopped short of granting a formal exemption.

Collyer also said the National Environmental Policy Act requires the Maritime Administration, known as MARAD, to conduct an environmental assessment of the risk posed in towing the ships overseas.

"This has not been done," the judge wrote.

But Collyer drew a distinction between the first four ships, which Congress had specifically authorized as a pilot program, and the remaining nine ships covered in MARAD's contract.

Collyer allowed for the export of the first four ships, noting that Congress called for "extraordinary expeditious decision-making" when it created the pilot program last year. But she blocked the export of any additional ships until at least Oct. 20, when a hearing will be held to further review the case.

With the exception of the pilot program, Collyer wrote, "there is no statute to excuse MARAD's failure to conform fully to the nation's environmental laws while exporting the remaining ships."

A MARAD spokeswoman said Thursday night the agency would have no immediate comment on the court ruling until officials can review it.

Environmental groups expressed both hope and anger at the judge's split decision. While hopeful that some ships may yet be blocked, they criticized the decision to proceed with a trans-Atlantic tow without additional review.

"It's hard to understand the Bush administration's rationale for placing the environment and ecosystems like the Chesapeake Bay at needless risk, when we have facilities in Virginia to recycle these ships safely," said Michael Brown, director of the Sierra Club's Virginia chapter, which claims 16,000 members.

The first two ships to travel to England- the Canisteo and the Caloosahatchee- could depart Hampton Roads as early as today, MARAD has said. The Coast Guard issued its approval for the towing Wednesday, a spokesman confirmed.

The ships, built in the 1940s, will travel across the Atlantic with 68 tons of solid PCBs, said Marcello Mollo, an attorney for Earthjustice, a public interest law firm representing environmental lobbies.

"We think it's outrageous the administration is bent on dumping those quantities on the U.K. public," he said, referring to the United Kingdom, where news of the pending ship-scrapping work has triggered environmental concerns.

MARAD issued a $17.8 million contract in July for the work, which will be conducted by the British scrapper Able UK. The deal included the sale of two uncompleted Navy oil tankers for $3 million. Domestic scrappers complained the contract was unfairly bid, but MARAD has defended the deal, saying it offered the "best value" to taxpayers.

After the Oct. 20 hearing, Collyer must decide whether to allow the rest of the ships to leave Hampton Roads or to issue a preliminary injunction blocking any more exports.

"Residents of the Tidewater region in Virginia would not be injured by a short delay in removing additional ships, as MARAD 'does not believe the vessels pose an imminent risk of harm,' " Collyer wrote.