Technicians continued yesterday to clean up the wreckage not just in the Howard Street tunnel, but on the information superhighway.

LAI Construction Services Inc. of Baltimore was completing yesterday a new fiber-optic loop around the downtown tunnel, where the CSX train derailment damaged cables that transport Internet data, e-mail and phone calls. Crews had nearly completed installing 30,000 feet of fiber when they were stymied by thick mud they discovered in underground ducts along Light Street.

Their work was crucial for Metromedia Fiber Network Inc. of White Plains, N.Y., and PSINet Inc. of Ashburn, Va., whose lines ran through the tunnel.

Another company affected, WorldCom Inc. of Clinton, Miss., reported yesterday that it had rerouted data and voice traffic elsewhere on its network and was not experiencing any more problems.

Meanwhile, Verizon Communications Corp. said that it restored phone service to two downtown office towers, 250 W. Pratt St. and 300 W. Pratt St., which had been flooded by a water main break believed to be caused by the fire in the tunnel. The buildings remained unoccupied yesterday.

A Silicon Valley company that tracks Internet traffic said Wednesday's train accident caused the worst congestion in cyberspace in the three years that it has monitored such data.

The link through Baltimore "is basically the I-95 of Internet traffic into and out of Washington," said Bill Jones, director of public services for Keynote Systems Inc. of San Mateo, Calif. This week's accident caused more disruption than an incident last winter when an act of sabotage against Microsoft Corp. tied up networks, he said.

The company, which monitors Internet flow by the hour on its Web site, said that the accident had almost no impact in some areas, including parts of Baltimore, while certain connections were 10 times slower than normal, such as the ones between Washington, D.C., and San Diego.

"There was a ripple effect around the country with corporate networks due to this Baltimore disaster," said Frank Stanton, an executive with Lexent Inc., a New York-based company that repaired fiber-optic cable after the World Trade Center bombing in 1993. "Everybody thinks they have redundancy, but these type incidents show people there are huge issues. When you cross rivers and bridges, these choke points are the Achilles' heel."