The Sudanese government may have suppressed information about the conflict. Some witnesses have been jailed, others may have been killed. This started in 2004. Also, some evidence, such as mass graves was tampered with, so that it became unusable. Some people say this was done by forces which are close to the Sudanese government. In addition, by obstructing and arresting journalists, the Sudanese government has been able to obscure much of what has gone on. The United States government has described it as genocide. The UN has declined to do so. In March 2007 the UN mission accused Sudan's government of "gross violations" in Darfur and called for urgent international action to protect civilians there.