Damage to a transmission line cut off most service to Arlington's 37,500 cable television subscribers from Wednesday afternoon until early yesterday morning, a spokesman for the cable company said yesterday.

Work crews traced the problem to an underground transmission line in the Virginia Square area near N. Nelson and N. 10th streets, said Eric McLamb, vice president for communications of Hauser Communications Inc., which owns Arlington's MetroCable.

The cable carries 25 of the 35 channels normally provided to subscribers, and company officials speculate that some of the office or residential construction in the neighborhood may have caused the damage.

"You don't necessarily have to come into physical contact with our equipment," said McLamb. The construction work "could have caused a short, could have caused a power surge," he said. "We may never be able to pinpoint" the cause, he said.

The breakdown occurred at 1 p.m. Wednesday and full service was restored at 3 p.m. yesterday. Partial service, at "50 to 60 percent quality," was restored at 1 a.m., he said.

About 8,100 customers called MetroCable on Wednesday and 5,000 phoned yesterday to inquire about the outage, McLamb said. The service interruption is the longest in the company's nine-year history of operations in the county, said officials of the firm.

The damage is unrelated to current work that will add 18 channels to the system, he said.

Company officials have not yet decided whether customers will receive a credit on their monthly bills to compensate for the temporary loss of service, McLamb added. "Before any credit is issued, the defective outage has to have occurred continually for 24 hours and has to be within MetroCable TV's control," said McLamb, noting that most service was restored in about 12 hours.