O'ahu's emergency call network crashed early yesterday, leaving the island without 911 service for more than 10 minutes.

More than 240 calls, many of them duplicates, were not processed during the outage but none of them turned out to be true emergencies, said Hawaiian Telcom spokesman Dan Smith. The cause of the outage is under investigation.

"We were really grateful to learn that there were no life-threatening situations," he said. "Still, we are very concerned that this happened at all."

Hawaiian Telcom turned over a list of phone numbers of all the people who tried to get in touch with police during the outage and police were able to determine that no real emergency went unattended, he said.

The 911 call center receives emergency and nonemergency calls.

The system went down at 9:57 a.m. yesterday and all emergency calls were rerouted to the military's emergency call center at Pearl Harbor at 10:10 a.m. The system was back online at the Honolulu Police Department's Alapa'i Street headquarters at 10:35 a.m.

Police spokeswoman Michelle Yu said 911 system problems are not common.

Reach Peter Boylan at pboylan@honoluluadvertiser.com.