Quicken Loans Inc. submitted insurance claims for hundreds of improperly underwritten U.S. Federal Housing Administration-insured loans over four years, the government alleged in a lawsuit.

Quicken’s deficient underwriting caused the Department of Housing and Urban Development to pay millions of dollars of insurance claims from September 2007 to December 2011, and the agency may have to pay more as other improperly evaluated loans go delinquent, according to the the False Claims Act lawsuit filed Thursday in Washington federal court.

The company “knowingly approved loans that violated FHA rules while falsely certifying compliance,” the U.S. said in its complaint.

Quicken last week filed a lawsuit in Detroit accusing U.S. investigators of improperly relying “on a skewed, cherry-picked and unrepresentative sampling” of FHA loans to build fraud allegations against the company. Quicken wants a court order barring the government from using the sample to evaluate compliance with U.S. underwriting rules.

An e-mail to Quicken’s media office wasn’t immediately returned.

The government case is U.S. v. Quicken Loans Inc., 15- cv-00613, U.S. District Court, District of Columbia (Washington). Quicken’s suit is Quicken Loans Inc. v. U.S., 15- cv-11408, U.S. District Court, Eastern District of Michigan, Detroit.