The Postal Service is looking into allegations that as many as seven truckloads of mail were removed from the Merrifield station, Northern Virginia's main processing center, so that it would not look backed up when Rep. Frank R. Wolf (R-Va.) visited there Monday.

Wolf has been investigating citizen complaints concerning delays in mail delivery in the area. This week his office received 30 such complaints, mostly from people who said their mail had been delivered late at night or delayed for days, said Edward J. Newberry, a spokesman for Wolf.

Lou Eberhardt, a spokesman for the postmaster general's office, said the trucks in question may have been on their way from the Merrifield station to a Largo processing center, as is their correct routine. But he added that the office would investigate the matter at Wolf's request.

Sources said the General Accounting Office has agreed to investigate the backup of mail at some Northern Virginia post offices. Newberry said Wolf's office has asked the GAO to give the Postal Service more time to straighten out the problems before it gets involved.

The volume of mail in Northern Virginia is up about 25 percent -- an additional 1 million letters a day -- over last year, local postal offices said. Neighborhood growth and early Christmas advertisements have been cited as the major reasons.

Newberry said residential and commercial growth in many Northern Virginia jurisdictions, especially in Herndon, McLean and eastern Loudoun County, had outpaced the service's delivery capabilities.

He said Wolf has asked the Postal Service to consider opening a Washington metropolitan postal division. Northern Virginia's mail service is currently supervised and directed from headquarters in Richmond.

"In Richmond, where there hasn't been a lot of growth, there's a different mind set," said Newberry.

Last month Wolf's office got in touch with postal officials in response to citizen complaints and was assured that evaluators would study long-term solutions.

Local post offices and union officials said letter carriers and clerks were working six days a week, 10 to 12 hours a day, to keep the mail moving. Fran Ford, public affairs officer at Merrifield, said last week that officials there are in the process of hiring about 200 carriers and at least 50 additional clerks for Northern Virginia post offices.