(CNN) -- The Egyptian prosecutor's office says evidence shows three suspects linked to al Qaeda targeted the U.S. and French embassies in Cairo, as well as an Egyptian army facility in the Sinai Peninsula, according to state news.
The state-run Middle East News Agency, known as MENA, reported Wednesday that state prosecutors have evidence suggesting the alleged terrorists, who were arrested over the weekend, planned to detonate car bombs at the three sites.
A source briefed by an Egyptian security official said Wednesday that he'd been told that France's embassy was allegedly targeted but was not told about the other diplomatic mission. Members of the alleged terrorist cell had 10 kilograms of ammonium nitrate, which is commonly used in bomb making, according to the source.
David Linfield, a spokesman for the U.S. Embassy in Cairo, told CNN that he's aware of reports in Egyptian media that the American embassy was targeted but otherwise had no comment on the matter. And an Egyptian Interior Ministry spokesman refused to comment to CNN about the alleged targets.
A prosecutor ordered one of those arrested, Mohamed AboulEla Aqida, to stay behind bars for at least 15 more days, rather than be put on house arrest, MENA reported Wednesday. The fate of the other two people detained was not immediately clear.
The prosecutor's office pointed to new evidence that has surfaced linking Aqida to a leading figure of al Qaeda in Iraq named Daoud Al Asdi, as well as al Qaeda members in the Sinai Peninsula, according to MENA.
He and others allegedly had gone beyond the planning stages and were getting ready to attack when Egyptian police arrested them, the source briefed by an Egyptian security official told CNN.
A U.S. State Department travel alert issued Wednesday did not specifically mention this plot, though it did allude to a May 9 knife attack on a U.S. citizen.
That American was outside the U.S. Embassy in Cairo, was asked if he was an American, then attacked. Egyptian police have a suspect in custody in that case, according to the State Department.
The diplomatic alert also urged Americans "to avoid all demonstrations in Egypt, as even peaceful ones can quickly become violent, and a foreigner could become a target of harassment or worse."