"We do not know where they are," Crowley told reporters. "We have not been informed by the Iranian government on that."
Crowley said that US officials have asked through the Swiss ambassador in Tehran, but "we have not yet received a response," he said.
The United States and Iran have no diplomatic ties.
Washington is demanding "in line with international agreements" that Iran "give us consular access as soon as possible," Crowley said.
Three US hikers, identified in the US media as Shane Bauer, Sarah Shourd and Joshua Fattal, went missing on July 31 after setting out from Iraq's northern Kurdistan region, on the poorly marked border with Iran.
Iran on Tuesday officially notified Washington about the arrest through Swiss channels, which represent US interests in Iran.
Crowley rejected Iranian charges of "meddling" in Iranian domestic affairs after the controversial June 12 presidential election.
Iran hardliners have accused opposition supporters, who poured onto streets to protest President Mahmoud Ahmadinejad's disputed re-election, of being backed and directed by Western powers, notably the United States and Britain.
"Obviously, Iran has just gone through an election," said Crowley. "It was Iran's election and clearly there was a result that even now … despite the inauguration of President Ahmadinejad, the people of Iran have questions about," he said.
