The State Department says it has been quietly offering rewards since January of up to $10 million for information about the attack last year on US diplomatic post in Libya.
In a letter sent to Congress Friday, the department says the rewards were not advertised on its website or posters or matchbooks as is usually done. That's because of security issues around the investigation into the attack on the mission in Benghazi that killed U.S. Ambassador Chris Stevens and three other Americans.
Lawmakers have complained the department is not using all the tools at its disposal to catch the perpetrators. The letter says investigators have other ways of publicizing the rewards.
The rewards are for information that leads to the arrest or conviction of anyone involved in the attack.