Montgomery County will conduct a review of its subdivision approval process after a planning department staff member improperly altered a site plan for a sprawling Clarksburg housing development, officials said yesterday.

The review, to be handled by an outside investigator, will focus on how hundreds of homes in Clarksburg Town Center were built in apparent violation of height and setback requirements and on whether similar problems exist in other subdivisions.

"We must take a hard look at our processes -- both internally and externally," said Charles R. Loehr, director of Montgomery County Department of Park and Planning.

A group of residents took evidence of violations to the Planning Board in April. The board found no wrongdoing, after reviewing a document in which the original height restriction of 35 feet had been blacked out and replaced by the words "four stories," or about 40 feet.

A few weeks later, a member of the residents group uncovered a copy of the original site plan, which stated that townhouse heights in the development were limited to 35 feet.

The staff member who presented the altered site plan to the commission, Wynn Witthans, resigned last week. She did not return several calls Wednesday and yesterday seeking comment.

Officials said that they have since identified 102 potential setback violations and that hundreds of townhouses might exceed height limits. A Planning Board hearing to consider possible sanctions against the builders and developer is scheduled for Thursday.

Clarksburg, in northern Montgomery, is contending with an explosion of county-sanctioned growth. Fueled by a robust housing market, the population has grown from about 2,000 to an estimated 5,500 over the last five years. Planners estimate that the town will be home to 41,000 people by 2025.

Because Clarksburg's growth has come so quickly, there has been confusion among officials about who is responsible for enforcing codes there.

The Park and Planning Department is supposed to inspect homes under construction for compliance with zoning laws and the county's master plan, according to county officials. The department, overseen by the County Council, is a part of the Maryland-National Capital Park and Planning Commission, an agency that serves Montgomery and Prince George's counties.

But planning officials said they had thought that the Department of Permitting Services, overseen by County Executive Douglas M. Duncan (D), was responsible.

"I was always told Permitting Services checks heights," said Rose Krasnow, chief of the planning department's development review division.

Charles Maier, a spokesman for the developer, Newland Communities of San Diego, said the company abided by all relevant laws. "We have built each and every home in strict compliance with government plans," Maier said.

Council members are demanding an investigation. "I believe the credibility of Park and Planning and all of these agencies are at stake," said County Council President Tom Perez (D-Silver Spring), who said the council could hold a hearing on the matter next month.

The alleged building and setback violations, first reported by the Washington Times, were uncovered by about 15 residents who formed the Clarksburg Town Center Advisory Committee after a dispute with the developer.

The residents, most of whom bought their homes in 2003, said they moved into the community after assurances that it would have a pedestrian-friendly town center with shops, cafes and an upscale grocery store. Instead, the residents said, Newland was trying to build a conventional suburban strip mall.

Concerned about the direction of their yet-to-be completed subdivision, they began to investigate. The group said it discovered that many townhouses were taller than the maximum 35 feet for single-family homes.

The group took the evidence to several county officials, including council member Michael Knapp (D-Up County), who contacted Derick P. Berlage, chairman of the Planning Board. Berlage told Knapp in a Dec. 23, 2004, e-mail that there were no height violations.

A spokeswoman for Berlage said he could not comment because of his role as a member of the Planning Board.

In an April hearing requested by the group, Witthans produced a site plan that had "35 feet" blacked out and replaced with "four stories." Board members, who declined to comment, ruled 4 to 1 that there were no height violations.

After a copy of the original site plan was found, the residents committee approached Loehr about the apparent discrepancy.

On May 10, Loehr left a phone message at the home of Amy Presley, a leader of the group. "Wynn did admit that she changed the drawing after you all brought the height issue to her," he says in the message, which Presley saved.

Although 35 feet was the prescribed height in the legally binding site plan, officials said, less formal staff reports put the limit at four stories.

Why Witthans might have doctored the plan remains a mystery. Council member Nancy Floreen (D-At Large) said Witthans was a longtime employee with a solid reputation.

"It's not like it's a person who's not familiar with the high standards of ethics," Floreen said.