Iranian state television is reporting that all 10 U.S. sailors detained by Iran after entering its territorial waters have been released. Iran's Revolutionary Guard said the sailors were released today after it was determined that their entry was not intentional.

TEHRAN, Iran — All 10 U.S. Navy sailors detained by Iran after drifting into its territorial waters a day earlier have been freed, the U.S. and Iran said today.

The Navy said the American crewmembers returned safely and there were no indications they had been harmed while in custody.

The nine men and one woman were held at an Iranian base on Farsi Island in the Persian Gulf after they were detained nearby Tuesday. The tiny outpost has been used as a base for Revolutionary Guard speedboats as far back as the 1980s.

The sailors departed the island at 0843 GMT aboard the boats they were detained with, the Navy said. They were picked up by Navy aircraft and other sailors took control of their boats for the return voyage to Bahrain, where the U.S. 5th Fleet is based.

The Navy added that it “will investigate the circumstances that led to the sailors’ presence in Iran.”

The Revolutionary Guard’s official website published images of the detained U.S. sailors before their release, showing them sitting on the floor of a room. They look mostly bored or annoyed, though at least one of the sailors appears to be smiling. The sole woman had her hair covered by a brown cloth. The pictures also showed what appeared to be their two boats.

“After determining that their entry into Iran’s territorial waters was not intentional and their apology, the detained American sailors were released in international waters,” a statement posted online by the Guard said Wednesday.

Vice President Joe Biden, speaking later to “CBS This Morning,” denied that Americans made any apology.

“There’s nothing to apologize for,” Biden said. “When you have a problem with the boat you apologize the boat had a problem? No, and there was no looking for any apology. This was just standard nautical practice.”

Gen. Ali Fadavi, the navy chief of Iran’s powerful Revolutionary Guard, was quoted earlier today by Iranian state TV as saying that an investigation had shown the Americans entered Iranian territorial waters because of “mechanical problems in their navigation system.”

U.S. officials also blamed mechanical trouble for the incident. They had said Tuesday that Tehran assured them the crew and vessels would be returned safely and promptly.