Nairobi, Kenya ? Somali pirates left two boats they had hijacked in the waters off the Horn of Africa, and the newly liberated vessels – and their crew of 24 – were under U.S. Navy escort on Sunday, the American military said.

A U.S. Navy ship and helicopter were guiding the Tanzanian-flagged boats Mavuno 1 and 2 farther out to sea, where naval personnel will later board the vessels and treat crew members, said Cmdr. Lydia Robertson of the U.S. Fifth Fleet in Bahrain. The Navy is in radio contact with pirates aboard three other ships in the region, encouraging them also to leave those ships and sail back to Somalia, she told The Associated Press.

“We’re very happy with this development and hope it happens with the other ships off the coast,” Robertson said. “We’re very happy for the crew and their families.”

Robertson said the pirates boarded skiffs after they left the hijacked ships, and headed back to Somalia. No shots were fired during the incident, she said. She gave no more details.

The U.S. has now intervened four times in one week to help ships hijacked by Somali pirates. Sailors boarded a North Korean ship to give medical assistance to crew members who overpowered their hijackers, and a Naval vessel fired on pirate skiffs tied to a Japanese-owned ship.

Robertson said that ship was still under control of pirates, although the U.S. Navy was still working to free that ship from pirates. There were no details on the other two seized ships. Hijackings in the vast stretch of water frequently go unreported.