Washington ? A U.S. contractor managing more than $1 billion in reconstruction contracts in Afghanistan faces federal criminal and civil investigations of claims that it overcharged the government for work, according to federal court documents.

Federal prosecutors are focusing on whether the Louis Berger Group, based in Morristown, N.J., submitted inflated invoices to the U.S. Agency for International Development, which oversees many of the government’s international development projects.

The allegations come as U.S. officials spar with Afghan President Hamid Karzai over allegations of corruption in his government. Karzai has questioned U.S.-led investigations of corruption in Afghanistan and argued that international donors have ignored corruption in billions of dollars worth of development projects they have handled.