HILO >> Hawaii County is continuing to test the reliability of its sirens after four tsunami sirens failed to pass the monthly test.

According to Hawaii County Civil Defense, warning sirens in Keaukaha, Punaluu, Naalehu and Ainaloa did not pass the test Monday, reported The Hawaii Tribune-Herald.

Two of the sirens had failed the test before, said John Drummond, an administrative officer in Hilo.

“There’s a lot of different things that can cause the sirens to not sound,” he said. “They’re mechanical devices out in the weather, so there’s a variety of factors that can cause (problems).”

A malfunctioning siren doesn’t always remain silent. Less than a year ago, Honomu residents were awakened early one morning when the area’s tsunami siren activated on its own. The siren sounded for half an hour before police dispatchers and Civil Defense workers managed to shut it down.

Drummond said Monday there hadn’t been any more “runaway sirens” as of lately.

Civil Defense tests the tsunami sirens in the morning on the first working day of each month. Also during that time, the state’s Emergency Alert System tests its audio broadcasts through radio stations.

The sirens can also be used to alert the public to terrorist incidents or acts of war.

In 2013, the state began a $25.6 million siren modernization program that instituted a new activation system based on cellular transmissions and satellite. The effort was meant to improve the system’s reliability.

Shelley Kunishige with the state Emergency Management Agency said the first phase of the program was recently completed, with the addition of 7 new sirens to the system.

“As of the latest update, we have 74 current sirens active in Hawaii County,” she said.

The second phase, planned for this summer, will add 25 new or upgraded sirens, and the third phase, scheduled for fall 2016, will add 42 additions and upgrades, she said.