Ten U.S. sailors are missing after a collision between the USS John S. McCain and a tanker early Monday east of Singapore, the second accident involving a ship from the Navy’s 7th Fleet in the Pacific in two months.The Navy said five sailors were hurt in the collision between the guided-missile destroyer and the 183-meter (600-foot) Alnic MC, an oil and chemical tanker. Four of them were evacuated by a Singaporean navy helicopter to a hospital in the city-state for treatment of non-life threatening injuries, and one did not require further medical attention.The McCain had been heading to Singapore on a routine port visit after conducting a sensitive freedom of navigation operation last week by sailing near one of China’s man-made islands in the South China Sea.The destroyer was damaged on its port side aft, or left rear, from the collision that happened at 5:24 a.m., the Navy’s 7th Fleet said, but was heading to port under its own power.One of the injured, Operations Specialist 2nd Class Navin Ramdhun, posted a Facebook message telling family and friends he was OK and awaiting surgery for an arm injury.He told The Associated Press in a message that he couldn’t say what happened: “I was actually sleeping at that time. Not entirely sure.”The Singapore government said no crew were injured on the Liberian-flagged Alnic, which sustained damage to a compartment at the front of the ship some 7 meters (23 feet) above its waterline. There were no reports of a chemical or oil spill.Singapore sent tugboats and naval and coast guard vessels for the search and rescue effort. Malaysia’s navy chief Ahmad Kamarulzaman Ahmad Badaruddin tweeted that two ships as well as aircraft from its navy and air force were helping with the search for the missing sailors. He tweeted a photo of the McCain that showed a gaping hole in its side near the waterline. The Navy said Osprey aircraft and Seahawk helicopters from the USS America were assisting in the search.There was no immediate explanation for the collision and the Navy said an investigation would be conducted. Singapore, at the southernmost tip of the Malay Peninsula, is one of the world’s busiest ports and a U.S. ally, with its naval base regularly visited by American warships.The collision was the second involving a ship from the Navy’s 7th Fleet in the Pacific in two months. Seven sailors died in June when the USS Fitzgerald and a container ship collided in waters off Japan.The Fitzgerald’s captain was relieved of command and other sailors were being punished after the Navy found poor seamanship and flaws in keeping watch contributed to the collision, the Navy announced last week. An investigation into how and why the Fitzgerald collided with the other ship was not finished, but enough details were known to take those actions, the Navy said.U.S. Senator John McCain of Arizona, the son and grandson of the admirals for whom the ship is named after, said in a tweet that he and his wife are praying for the ship's sailors.Responding to questions from the press about the incident, President Donald Trump said, "That's too bad." He later said on social media that his thoughts and prayers are with the ship's sailors.The McCain, nicknamed "Big Bad John," has a crew of dozens of officers and chief petty officers and around 291 sailors. Its home port is in Japan.The Associated Press contributed to this report.