The state-linked newspaper al-Watan reported Saturday that eight Americans had been detained in the past three months on terrorism-related crimes.
The list of detainees in the Arab kingdom is frequently updated and posted on the Interior Ministry's Nafetah website, which helps relatives to communicate with prisoners. The list includes 5,158 detainees, mostly Saudi nationals.
Four Americans were arrested in November and December and another four were detained on January 25, according to the site. A ninth US citizen was arrested in March 2007 and convicted, though the site does not provide details.
The names, ages, genders and other personal details of the US detainees are not listed.
US State Department spokesman John Kirby on Monday said officials are looking into the arrests.
"I just don't know at this time how true that posting is," he told reporters in Washington. "We are working closely with Saudi authorities to try to figure this out."