The Justice Department filed suit Monday contending that Culpeper County, Va., acted in a discriminatory manner in denying an approval needed for the construction of an Islamic house of worship there.

Justice asked a federal court to order the largely rural county to grant the permit approval needed by the Islamic Center of Culpeper for its proposed mosque. About 12 to 20 Muslims have been showing up for prayers at a temporary site, and wished to build a permanent home for their activities.

No mosque exists in the county, which is about 70 miles southwest of Washington. The nearest is 45 minutes away by car, Justice said.

The vote that has prevented construction came on what appeared to be a narrow technical question regarding the disposal of sewage. But the Justice Department investigated the issue with an eye toward determining whether the refusal of a disposal permit involved religious discrimination.

In its lawsuit, the department based its argument on the Religious Land Use act, which was intended to protect religious freedom and prevent discrimination in the application of land-use laws to places of worship.

The Islamic Center was told by the county health department, according to the lawsuit, that conditions at the proposed site required sewage removal by what is known as the pump-and-haul method.

In pump-and-haul, sewage is stored on site and trucked away periodically for treatment, a process that required a permit, according to the lawsuit.

In its suit, the Justice Department’s civil rights division said rejecting the request for the permit made building the mosque impossible. As a result, the department argued, the Islamic center’s members “cannot engage in their religious practices to the degree and in the way they believe they are compelled to do.”

The department said no other suitable land was available for the mosque. It argued that the board made use of the pump-and-haul permit process as a means to bar a use that the board “did not want.”

The lawsuit asserted that permission had been approved in cases similar to the Islamic center’s.

A large crowd at an April meeting cheered the introduction of the motion to deny the permit. The supervisors rejected the permit by a 4-to-3 vote.

After learning of the Justice Department’s review of the matter, County Administrator John Egertson had expressed confidence that the study would show that the county was “completely compliant.”

He said the board “acted within their policy, and they acted fairly and consistently.”

In an interview Monday night, William C. Chase Jr., the supervisor who proposed denial of the permit, called pump-and-haul a “very messy operation.”

He said the vote “had nothing to do with religion” nor did it depend on “who it was making the request.” Instead, he said, it was based on county permit practices.

County attorney Bobbi Jo Alexis said the county considered the lawsuit “ill-informed” and intended to defend its actions vigorously.

She said the county had based its actions on health concerns rather than on questions of religion. In a letter sent last week to Justice, she wrote that pump-and-haul of sewage could cause contamination.

She also said the Islamic Center did not show the supervisors that it had addressed alternatives to pump and haul.