Two members of the US Coast Guard in Alaska have been found dead, prompting concerns that a killer could have struck at a remote island outpost. A captain at the Kodiak Island Station said they were unsure what happened and a suspect could still be at large. The base and schools in the area were put on lockdown and residents of the island were told to remain vigilant. The names of the victims will be released after their families have been notified, the coast guard said. "It is possible that the suspect remains at large," Commanding Officer Captain Jesse Moore said. "Since we don't have all the details, we strongly advise all Kodiak residents to remain vigilant and to report any suspicious activity to local law enforcement officials." The captain also said the unit was "deeply saddened" to have lost two shipmates. Officials were unable to determine whether the deaths were a double murder or a murder-suicide. "This is a rare occurrence and we are going to do everything possible to ensure we find out exactly what happened," he said. Agents from the FBI have been sent to Kodiak from the town of Anchorage, about 250 miles (402km) away. Kodiak has a population of about 6,300 people.