A bomb threat that closed the Martha’s Vineyard Airport for some three and a half hours Tuesday morning remains under investigation by police.

The airport was cleared to reopen just after 9:30 Tuesday morning, following an intense sweep of the area by local and state police and a bomb-sniffing dog that was flown in by helicopter.

Bomb-sniffing dog was flown in by helicopter. — Holly Pretsky

The threat was made by telephone at 6:06 a.m., West Tisbury police said later in an official statement. Airport officials said the call lasted a few seconds and was recorded.

Police were notified immediately; the airport was closed and its building evacuated. Massachusetts state police, along with West Tisbury and Edgartown police and fire departments all responded.  The Salvation Army was also on the scene providing assistance.

A sweep of the premises was completed without incident, the statement from West Tisbury police said. 

The airport was reopened at 9:40 a.m.

West Tisbury Sgt. Matt Gebo and Edgartown Sgt. Michael Snowden were among the first responders on the scene.

During the closure all outgoing flights were cancelled and all incoming flights were rerouted.

Traffic into the business park was allowed, but travelers arriving for outgoing flights were being turned away.

Police set up a command center near Vineyard Decorators. West Tisbury police chief Matt Mincone was the incident commander.

The investigation is ongoing, police said.